Clinical trials and double blind method.

When choosing and comparing products or technologies, most people - it just so happened - are usually guided by the opinion of competent experts. And the experts, in turn, are guided by their experience and their own preferences. However, there are other, much more objective evaluation criteria, which often give very unexpected results. A clear illustration of what can serve as recent tests that compared, in one case, the quality in different ways compressed audio recordings, and in another case - the quality of printer printing with different inks and paper grades.

An honest path to truth

The so-called double-blind testing method came from science, where it is very important part research tools of scientists, because it allows you to get the most objective results of experiments involving people. The purpose of the double-blind method is to effectively neutralize the initial subjective biases and shifts in opinion that are always characteristic of both the test subjects and the organizers of the experiment, and therefore explicitly or implicitly affect the analysis of test data and the evaluation of the final results. Today, this method is considered one of the most important in many serious areas of research from medicine and psychology to sociology and forensics.

What is a blind testing method in principle, it is very easy to explain by the example of tasting, say, tea. At open method tastings invited consumers taste the tea different brands and firms in conditions where the belonging of the contents of each cup to a certain brand is known in advance, and therefore tasters usually choose those names that they use regularly or at least know something about them. From experiments it is well known that if, when tasting the same drinks, all information about brands is hidden, then the same subjects often choose a completely different brand. In other words, the blind method helps to remove conscious or subconscious shifts in the subjects' ideas that significantly affect the outcome of the experiment.

In more serious scientific trials like medical trials, when it's not about liking or not liking a drug, but how effective it helps in treating, one of the generally accepted methods of testing is called single-blind, that is, single-blind. In this method, each subject does not know whether he or she is in the test group taking the new drug, or in the control group, which is given something neutral to compare the results with the test. But, as experience shows, this method is not very good, because the experimenters themselves are also people and, when organizing experiments, voluntarily or involuntarily try to influence the desired outcome. So, say, patients can often guess whether they are being given a pacifier or a real medicine. More a prime example the same is the procedure for identifying a criminal by a witness, when the organizers of the identification know in advance who needs to be exposed, and a seemingly impersonal method is arranged in such a way as to push the subject to the desired choice.

To eliminate all such distortions, a double-blind (double-blind) testing method has been developed, in experiments with the participation of people, which makes it possible to effectively neutralize the subjective prejudices of both the subjects and the testers themselves. Under double-blind conditions, neither the subjects nor the experimenters know who is a member of the test group, and who is a member of the control group for comparison (in law enforcement conditions, when the organizers of the identification themselves do not know who the alleged criminal is). Only after all the test data is recorded (and in some cases after it has been analyzed) do researchers finally get information from an independent third party about who was who. With careful organization and random distribution of subjects into testing and control groups, the double-blind method allows you to completely get rid of human subjectivity and is carried out in cases where you want to achieve the highest standards of scientific rigor.

Although double-blind methods are most widely used in medicine, in principle they can be used in any experimental situation where there is a possibility that the test results will be influenced by conscious and/or subconscious shifts in the ideas of the participants in the experiment. It is especially convenient to arrange double-blind tests with the help of a computer, since the program organizing the experiment can be easily made so that it does not have any shifts in favor of one or another choice. By analogy with the above examples from medicine and forensics, the part of the program that provides interaction with the person being tested is the experimenter working blindly, and the part that knows exactly what is proposed for evaluation is an independent third party.

A classic, one might say, example of such an approach, often implemented using a computer, is the so-called ABX test, where the test person is offered an unknown stimulus X for testing, which should be attributed to one of two possible and already known choices A or B. In addition, that this test is very easy to organize in various modifications, ABX has long been famous for the fact that it easily and clearly debunks persistent myths that exist among the population. For which, to put it mildly, he is disliked by many authoritative experts who create these myths.

Ears are confused

In the 1990s, when the public began to master the mass compression of music from Audio CD to MP3 files, no one at first had the idea that the compressed audio tracks and the original CD tracks sounded equivalent. The generally accepted compression standard at a constant bit rate of 128 Kbps yielded approximately a 10-fold savings in file size, making it possible to transfer music through a narrow channel of a telephone modem, while maintaining a fairly acceptable sound quality for listeners. But no more.

However, the speed of Internet connections increased noticeably over the years, the capacity of computer hard drives grew even faster, and in parallel with them, the bitrate of audio file compression also increased, giving tangible improvements in sound quality, but at the same time increasing file size. Therefore, at some stage of this process, an inevitable question arose: at what values ​​of compression parameters does an increase in bitrate cease to justify itself in terms of sound quality, but only entail an increase in disk space for storage? Perhaps, in most cases it is reasonable to stop already at 160 or 192 Kbps? And with a bitrate of 256 or 320 Kbps, the tracks sound so clear that, perhaps, already seasoned audiophiles are not able to distinguish them from uncompressed CD sound? Not to mention ordinary music lovers…

Genuine audiophiles, usually scornful of all these MP3s, tend to strongly object to compression and are confident that they will always distinguish lossy compressed sound from the original. However, back in the spring of 2000, the German computer magazine c't conducted a very high-quality double-blind test of MP3 and CD tracks with the participation of a dozen audiophiles selected by a professional commission from several hundred applicants. The results of the tests greatly surprised everyone - both the participants and the organizers. When listening to 1-minute fragments from 17 pieces of classical, jazz and pop music, presented in three versions (128 Kbps, 256 Kbps and CD-quality), the subjects quite confidently allocated only 128 Kbps, but when assessing 256 Kbps and uncompressed tracks, the results with the best quality selection turned out to be absolutely identical. In other words, in exactly half of the cases, listeners preferred CDs, and in half the cases, MP3 256 Kbps tracks. Gernot von Schulzendorf, a Deutsche Gramophon sound engineer invited as a reference listener, who is preparing for the publication of master copies of classical music recordings, in general tests did not participate, but in preliminary tests with the identification of CD-sound, it showed noticeably better results than the others. After the end of the tests, Schulzendorf revealed the secret of his success. It turned out that he knew from experience that many recordings of certain genres with high-quality compression sound more rounded and more pleasant to the human ear than the original CD track. Therefore, in a number of cases, he made his choice analytically, in fact, in defiance of what his ears really hear.

The interesting results of c't were discussed a lot on the Internet at one time, but it cannot be said that they shook the point of view of real audiophiles, who continue to firmly believe in their rightness. And now insisting on the indisputable superiority of those formats, like FLAC, that for the player and computer they can pack audio recordings with lossless compression (that is, when playing, restoring the file to a full copy of the CD track). However, undeniable progress has been made in lossy compression algorithms, where the same MP3 with a variable bitrate can now simultaneously provide both the highest compression and best quality for a predetermined bitrate base. In other words, the long-awaited question about the value of the parameter at which it is reasonable for lovers of quality to stop increasing the bitrate, knowing that the human ear can no longer catch the subtlest differences, has not lost its relevance.

A very recent double-blind test on this subject in April 2007 was conducted by the American magazine Maximum PC. Here the experiment was set up like this. Four audiophiles were invited to a computer with a high-quality Creative X-Fi audio card and decent Sennheiser HD 580 headphones, each of whom brought his own CD with a reference track, where the nuances of the sound picture, in their opinion, are best suited for analyzing the quality of compression. Each such track was presented for listening in three quality levels - 160 Kbps, 320 Kbps and uncompressed WAV. Moreover, the compression was carried out with a variable bitrate (VBR), when the degree of compression dynamically decreases or increases depending on the complexity of a particular musical fragment. Thus, each tester was provided with a total of 12 tracks for comparative listening in the most friendly conditions. That is, the ranking of records by quality was carried out not on the basis of a minute excerpt from each piece, but when listening for any time interval, any number of times and with the possibility of alternate (A / B) comparison with other tracks.

Most of all, absolutely all audiophile testers were amazed at how difficult the task turned out to be in reality. It turned out that when the lower compression threshold is raised to 160 Kbps VBR quality, the audio track becomes very, very difficult to distinguish from CD quality even for an experienced ear. Not to mention the bitrate of 320 Kbps. Summing up the general result of this test, it can be noted that under conditions when the maximum possible number of correct quality identifications was 12, the most best result correct guesses for one audiophile was 6, that is, only half. If we slightly change the calculation method and take into account that each of the 4 testers listened to 4 tracks as a CD for analysis (that is, 16 in total), but at the same time they correctly identified the uncompressed quality only in 6 cases, it turns out that in 10 out of 16 listening sessions, MP3 files were found to have the best sound quality. Indeed, there is something to marvel at both audiophiles and ordinary MP3 lovers.

The letter X and the letter E

The impressive progress made by the printer industry over the past decade and a half has brought relatively inexpensive devices into the home that produce very high-quality color printing that consumers could not even dream of in the early 1990s. Perhaps the only thing that causes grumbling and growing bewilderment is the price of consumables, especially the quickly running out of printer ink. While the advantages of the printers themselves are growing from year to year, and their prices are decreasing, the cost of ink and paper for these devices remains practically unchanged, which is why home printing continues to be an expensive, generally speaking, pleasure.

The fact that the prices of branded ink and paper produced by the same company that manufactured the printer are artificially inflated has long been no secret to anyone. It is for this reason that ink and other consumables from third-party manufacturers are becoming increasingly popular among the people. For significantly less money, you can buy about the same consumables from them, which in appearance give the same result as branded goods. However, almost every buyer of a left-handed product has a doubt in his soul - is the print quality falling too much in comparison with branded materials? Moreover, manufacturers of native (expensive) ink-paper regularly press on this circumstance.

In order to bring clarity to such pressing issue, the American publication Trusted Reviews, which specializes in reviews and tests of consumer computer technology, conducted a large (double-blind, of course) comparison of printer consumables from all four major manufacturers. Each of these companies is well-known to consumers, but the rules established for some time in the computer press are such that it has become economically safe to explicitly indicate the name of the company only in cases where the material is obviously laudatory. This study clearly does not apply to such cases, so the famous printer manufacturers will be mentioned only with transparent allusions - to the letter C, to the letter E, to the letter H and to the letter L.

So, the question posed by the researchers was very simple: how does the quality of printing based on consumables from third-party manufacturers compare with printing with branded ink and paper? Four popular modern printers widely used by home users were selected for testing (exact model names can be found in the final report at www.trustedreviews.com). The most well-known US companies Cartridge World, InkTecShop, JetTec and StinkyInk were chosen as third-party ink suppliers, but these names do not play a significant role, since companies of this kind usually import, refill and resell consumables from a variety of manufacturers. The only important thing is that it is an abundantly offered cheap alternative to expensive branded materials.

The second, no less significant aspect is the choice of paper. All printer manufacturers insist that the two main components, ink and paper, must be developed together to ensure high-quality printing. The chemistry of the ink must match the characteristics of the paper, so the structure of printer paper has several layers of different materials- one absorbs ink, the other prevents it from spreading, the third provides gloss to photographs. To test the truth of the thesis about the importance of matching branded paper with its ink, the researchers collected sets of glossy photo paper from four printer companies, and for comparison - packs of universal printer paper from third-party suppliers: Ilford, Kodak, PC World and Staples. To print not photos, but ordinary documents, they took a pack of ordinary office paper for printers and copiers.

Testing consisted of comparing three types of images: a page of black text and graphics on a white background, and two photographs. One is a landscape with green trees, blue skies and a rocky coastline of red granite. The second is a photo of the model, which gives various shades of body color and the texture of clothing fabrics against a green background of foliage. These samples were printed on all four printers, with five types of ink and six types of paper.

The resulting 250 prints were submitted to a panel of typical and reasonably experienced users who were asked to rate each image on a 10-point scale. The guidelines for evaluation were as follows. 10–9 points - if the quality of the picture is such that it would be desirable to leave it as a memory of a wedding, anniversary or other important event in life; 8-7 points - as a memory of the vacation; 6-5 points - good enough to just leave a picture, albeit with small defects; a smaller number of points is for pictures that you are unlikely to want to save because of poor quality.

Before being issued for evaluation, all printouts were numbered and thoroughly mixed, so that, in accordance with the double-blind method, neither the evaluators nor the organizers had any idea what kind of printer, ink and paper were used in a particular case. The common conclusion of all evaluators after testing is that the task of finding differences is extremely difficult, since all printouts of the same picture had very similar quality. However, when all the test results were neatly listed in tables, in which the parameters of each printout were restored by numbers, the characteristics that scored the most points were easily identified.

The most important result of the test is that the members of the evaluation committee as a whole clearly preferred those printouts that were made using third-party consumables. For each printer individually, left-handed ink and paper combinations from different vendors scored higher than prints using a combination of branded cartridge and branded paper.

Thus, it became possible to quite competently and scientifically justify asserting that third-party inks are in no way inferior to branded inks in terms of print quality. consumables, and with a particularly successful combination of components, they can noticeably surpass them. But this, it should be noted, is not yet the whole picture in its entirety. Because every major printer manufacturer also claims that left-handed ink fades significantly faster than their own. And from here the continuation of the Trusted Reviews test naturally follows. Now the samples reproduced for the first study are partly pasted on the glass windows, partly on the walls and bulletin boards inside the building, and the rest are placed in an album on a shelf in a closet. About six months later, the organizers of the test will return to them and see how true the idea of ​​​​the firmness of branded inks is. It is quite possible that this result will not correspond to the popular opinion.

Not all ideas that scientists use in their work are suitable for general use. We should be primarily interested not just in research methods, but in tools that will help non-scientists better understand what science is and make more informed life decisions. Why do three-quarters of Americans believe in angels and hell, half in ghosts, and a third in astrology? Why does a quarter of Americans believe that the president of the United States was born outside the country and therefore cannot hold office? Why do two-fifths of Americans believe that the universe appeared later than man tamed the dog?

Let's not be defeatists who blame human stupidity for everything. This is probably partly true, but let's be a little optimistic and imagine that everything is fixable: it's just a lack of critical thinking skills, an inability to separate personal opinion and prejudice from evidence. I believe that a double-blind controlled experiment is capable of instilling them - a kind of scientific double-edged sword, but in good sense. On the one hand, this is an excellent research tool: initially, not only the subjects, but also those people who directly conduct the experiment do not have full knowledge about the nuances of the experiment, which allows minimizing the subjective factor, in addition, there is a control group that helps to check objectivity of the obtained results. On the other hand, it is also an excellent educational, didactic tool with which you can teach people critical thinking. My idea is that you don't actually need to do double-blind controlled experiments to achieve this. One must understand the principle itself, grasp its importance and enjoy its elegance.

If every school taught children how to do double-blind controlled experiments, our thinking would improve, and in these areas:

1. We would understand that it is not worth making generalizations based on anecdotes - isolated cases.

2. We would understand how to evaluate the likelihood that an effect that seems important is actually the result of pure chance.

3. We would understand how difficult it is to exclude bias in mental constructions, which is far from always the result of dishonesty or corruption of any kind. This is a very important lesson. It has an extremely beneficial effect in regard to distrust of authorities and personal opinion.

4. We would understand that we should not succumb to the temptations of homeopaths and other scammers and charlatans who would remain out of work.

5. We would understand that we need the habit of critical and skeptical thinking, which in the end can save the world.

What is the blind method?

blind method- the procedure for conducting a study of the reaction of people to any impact, which consists in the fact that the subjects are not initiated into the important details of the study. The method is used to exclude subjective factors that may affect the result of the experiment.

It lies in the fact that not only the subjects, but also the experimenters remain unaware of important details experiment until its completion. The double-blind method eliminates the unconscious influence of the experimenter on the subject, as well as subjectivity in the evaluation by the experimenter of the results of the experiment.

The blind method has become widespread in medical testing. To obtain objective results, patients are divided into two groups; one group receives the new drug and the other, the control group, receives a placebo. At the same time, patients do not know which of them is in the control group. This eliminates the so-called "placebo effect", which consists in the fact that the patient's condition may improve simply because of what he thinks he is taking. effective medicine(on average, this occurs in 5-10% of patients). Although this method increases the objectivity of the study, it does not exclude the subjective assessment of the patient's condition by the doctor conducting the study. In the case of a double-blind method, the doctors directly involved in the trial also do not know which of the patients they are giving the drug and which the placebo.

The application of the method is not limited to medicine, it can and should be used in any cases where the subject or experimenter can consciously or unconsciously influence the result. For example, it is quite obvious that when conducting an expert evaluation of a project, the expert, in order to maintain objectivity, should not know who the proposal comes from. However, the organizers of the tender can also influence the result by choosing a certain expert to evaluate a certain project. Therefore, it is important that this choice is also made blindly.

The double-blind method is also used to scientifically test claims of paranormal abilities, such as the ability to read minds or determine the color of objects without the aid of sight (skin-optical perception).

Richard Dawkins is a biologist, professor at Oxford and Berkeley, and a member of the Royal Society of London for the Advancement of Natural Knowledge about what is useful to know about life if you use the most ordinary scientific procedure.

“Not all ideas that scientists use in their work are suitable for general use. First of all, we should be interested not just in research methods, but in tools that will help non-scientists better understand what science is and make more informed life decisions. Why do three-quarters of Americans believe in angels and hell, half in ghosts, and a third in astrology? Why does a quarter of Americans believe that the president of the United States was born outside the country and therefore cannot hold office? Why do two-fifths of Americans believe that the universe appeared later than man tamed the dog?

Let's not be defeatists who blame human stupidity for everything. This is probably partly true, but let's be a little optimistic and imagine that everything is fixable: it's just a lack of critical thinking skills, an inability to separate personal opinion and prejudice from evidence. I believe that a double-blind controlled experiment is capable of instilling them - a kind of scientific double-edged sword, but in a good way. On the one hand, this is an excellent research tool: initially, not only the subjects, but also those people who directly conduct the experiment do not have full knowledge about the nuances of the experiment, which allows minimizing the subjective factor, in addition, there is a control group that helps to check objectivity of the obtained results. On the other hand, it is also an excellent educational, didactic tool with which you can teach people critical thinking. My idea is that you don't actually need to do double-blind controlled experiments to achieve this. One must understand the principle itself, grasp its importance and enjoy its elegance.

If every school taught children how to do double-blind controlled experiments, our thinking would improve, and in these areas:

We would understand that it is not worth making generalizations based on anecdotes - isolated cases.

We would understand how to evaluate the likelihood that an effect that seems important is actually the result of pure chance.

We would understand how difficult it is to exclude bias in mental constructions, which is far from always the result of dishonesty or corruption of any kind. This is a very important lesson. It has an extremely beneficial effect in regard to distrust of authorities and personal opinion.

We would understand that we need a habit of critical and skeptical thinking, which in the end can save the world.

blind method - the procedure for conducting a study of people's response to any impact, which consists in the fact that the subjects are not initiated into the details of the study. The method is used to exclude subjective factors that may affect the result of the experiment.

lies in the fact that not only the subjects, but also the experimenters remain ignorant of the important details of the experiment until its completion. The double-blind method eliminates the unconscious influence of the experimenter on the subject, as well as subjectivity in the evaluation by the experimenter of the results of the experiment.

By the way! This type of control is often used in drug studies where neither the subject nor the person using the drug knows whether it is a drug or a placebo. In this case, the effects can be separated medicinal product from any preconceptions about what effect the drug should or should not have.

In medicine, when testing the effects of new drugs - does it really work or not? - use double blind method: this is when neither those who are being treated, nor even those who are treating, are aware of what kind of medicine they are giving to a particular patient: a real one or a “dummy” (placebo). Still unclear? Let's deal with Masha and Vasya!

A steaming bowl of soup stood silently in the middle of the table and attracted all eyes.

Vasya, - Vasya's mother repeated doomedly. - There are no carrots there. Eat please.

If only Masha would be ashamed, - said mother, and Vasya and Masha were both embarrassed.

There was a long pause, during which both Vasya and Vasya's mother felt terribly sorry. Masha realized that it was time for her to intervene. No wonder he and Vasya had definitely decided to devote themselves to experimental science.

Vasya! she said decisively. - You claim that you can smell the carrot smell in this soup.

Yes, - looking at the table, Vasya answered gloomily.

And you, Aunt Marina, say that you didn’t put carrots in this soup.

Okay, - said Masha cheerfully. - We can no longer check if there were carrots in this soup, but we can check something else. Namely: can Vasya smell the boiled carrots. If it can, then there were carrots in the soup, here!

How will we do it? Vasya asked sullenly.

Very simple. Do you have carrots in the house? - Masha asked Aunt Marina.

There is, of course, - answered Vasya's mother, pointing her chin at the refrigerator. Vasya shot her an accusing glance.

Then we'll do this. Now, - Masha jumped up from the table, pulled out a bag of carrots from the refrigerator and took out one carrot from it, - we will cook this vegetable. Pour the broth into a glass, pour into another glass clean water, blindfold Vasya and let him smell both liquids and compare.

What if I'm wrong? Vasya muttered without looking into Masha's eyes.

Then eat the soup like a pretty one.

What if he's not wrong? Vasya's mother asked.

Well, then you will have to admit something, - Masha said embarrassedly.

And if Vasya guesses RANDOMLY? - Vasya's mother was indignant. - Just think, he will say at random - yes or no, but it turns out that everything is so?

Taak, - answered Masha thoughtfully. - This is problem.

And everyone thought.

ABOUT! - Vasya unexpectedly answered (by his tone, Masha immediately realized that the capricious child in him had given way to a real scientist). - I can sniff these liquids not just once, but many times. Once I may say the correct answer by accident. But if I sniff a hundred times, and every time I guess, then, mommy ... - (and the real scientist again gave way to a capricious child).

Fine! - said Masha and began to peel the carrots.

Stop, - said Vasya's mother. - And what will we do if Vasya says every time that there are carrots. He will, of course, tell the truth every time the carrot is there. But the fact that there are no carrots there, - and mother cast a bitter look at a bowl of soup, - he will never guess.

Okay, - Masha put down the carrot and the knife and took a sheet of paper. - Let's write it down.

And she made a simple table:

Vasya, who had been looking over Masha's shoulder all this time, snatched the paper from her and redirected "Vasya is just showing off" to "Vasya is delusional".

Misguided - so misguided! Masha readily agreed. - Well, let's start the experiment, shall we? If Vasya answers correctly all the times, then ...

No, Vasya said suddenly. - Suddenly I feel carrots, but not always? Its smell is weak, you can make a mistake. If I answer correctly half the time, will it count?

Not enough yet, - his mother immediately responded. - Half the time you can answer correctly, even if you don't feel anything at all. Even if you just randomly say anything, in half the cases you will answer correctly simply according to probability theory.

Okay, - Vasya said humbly, - and what figure do you think is correct?

Well, uh, - mum thoughtfully, - for example, if you answer correctly at least ninety percent of the time ...

At sixty! Vasya retorted quickly.

At eighty! his mother replied.

At seventy! they said in unison.

Well, no, - unexpectedly said Masha, who was tired of turning her head from one to the other, like at a tennis match. - It is not right. There is no such boundary between "yes" and "no". If 50% - it means that Vasya definitely does not understand. If 100% - exactly understands. And the rest - it's so blurry. Rather yes than no, or, conversely, rather no than yes.

That's right, Mom agreed. - But Vaska and I need to agree, 70% of both of us are satisfied, right?

Yes! Vasya responded bravely. - Boil carrots already and come here, I'll sniff.

Eh no! Vasya's mother suddenly said. - Do I know you. If Masha gives you a sniff, she will prompt you.

I won't! Masha was indignant.

Mash, - Vasya's mother said softly. - I don `t want to offend you. It’s just that you will root for Vasya, and, well, I don’t know, poke a glass of water right under his nose, and take a glass of carrot broth away from his nose, well, or somehow else, I don’t know. And so Vasya will guess what is in this mug - not by smell, but by your prompts. Of course, this is not on purpose - it happens by itself, doesn't it?

Masha lowered her eyes to the table in embarrassment: it was true.

Then you, mother, offer me a mug yourself, ”Vasya said gloomily.

No, that doesn't work either, - Vasya's mother answered. - I am also an interested person. I will also do the opposite. Do you know what we'll do? We use a double blind method.

Like this? Vasya and Masha were surprised together.

Well, we won't have to go blind, - my mother winked. - This expression came from medicine. The fact is that when a patient is given a medicine, he, as it were, tunes in to recovery and as a result recovers - but not because of the medicine, but because his body has mobilized. Even if a person is given a pill that does not contain any active ingredients, well, just sugar in a tablet shell, and is told that this is a miracle drug, he will feel relief. This phenomenon is called the "placebo effect". "Placebo" means "dummy" in Latin. In principle, the placebo effect is great, it kind of helps the drugs work. But if the drug is new and we are only conducting clinical trials, checking whether it is good or not, then great difficulties can arise. Here we give the patient this medicine, we see that he has become better and we conclude that the medicine is useful. What if it's not like that at all? What if the drug is actually harmful, and the patient got better because of the placebo effect? How to understand what the medicine really costs?

Well, - answered Masha, - you just have to not tell the patients that they are being treated. Sneak medicine into them, like... like carrots in soup.

In response to this remark, Vasya silently incinerated Masha with a look, and then said:

Yes, you just need to take two patients. Or not, not even two patients, but two groups of patients, that's it! And tell all patients that they are given medicine. But in fact, some are given real medicine, while others are just empty pills. And then see which group recovered better.

Great, son! Vasya's mother said. - That's how they do it in medicine. It is called blind method. The patient is as if blind, he does not know whether he is receiving medicine or a dummy. Therefore, both groups of patients will have the same placebo effect, but the drug will act only on one group. But there is a problem here too. Studies have shown that if the doctor knows that he is giving the patient real medicine, then he, as it were, transfers this knowledge to the patient. Of course, he will not tell him anything, but he will behave in such a way that the patient himself will guess that he has already got something that will really work. Well, that's like Masha, who would slip Vasya a carrot with a completely different gesture than some water. The placebo effect in this patient will become stronger, and again we will not be able to find out what the medicine really costs. How to deal with this problem?

- double blind method! - Masha blurted out as soon as possible, so that Vasya did not have time to interrupt her. - We will make sure that the doctor was also, as it were, blind! So that he does not know what medicine he gives to the patient. Let it be written somewhere which patient got what, and let the doctor not know this. He just gives all patients seemingly the same medicines - but one is real, and the other is a dummy.

Right! Well done, Masha! That is exactly what we will do. Vasya will be like a blind man, because we will blindfold him. And instead of the second blind man, we will have Uncle Misha, who does not know at all what we are doing here. Vasya, so that dad does not understand what we are doing here, and does not begin to influence the results, answer only yes or no. Yes - carrot broth, no - water. Agree?

Vasya nodded.

Wonderful! Mom said. - Mash, cook carrots!

Masha cleaned the carrot, threw it into a pot of water and put it on the fire. Mom at that time put the kettle on so that a glass of clean water, as hot as carrot broth, would be ready at the right time. Masha stood on tiptoe and took two identical opaque cups from the shelf. Mom, blocking herself from Vasya, wrote in advance on a piece of paper the sequence in which mugs of water and carrot broth would be served - so that this sequence could then be compared with Vasya's answers. Vasya looked at all this at once, both as a researcher and as a guinea pig - until his mother blindfolded his eyes with a scarf.

Miiish! she called into the other room when everything was ready.

Vasya's father appeared on the threshold. He glanced at the bowl of soup that everyone seemed to have forgotten about and said:

No, that's not the point, - Vasya's mother responded. - That is, Vaska, of course, does not eat soup. But we are now just sorting out whether he has the right to do so.

Vasya's father silently and questioningly looked around those present. He stared at the blindfold over Vasya's eyes for the longest time and most perplexedly.

You, most importantly, do not try to understand anything, - said Vasya's mother and blindfolded Vasya's father. - Now I will give you mugs with liquids, and you pass them to Vasya, and then back to me. Mash, get ready to write down Vasya's answers.

She consulted her paper, chose one of the mugs and handed it to Vasya's dad. Vasya's dad, blindfolded and with an impenetrable face, shoved the mug right under Vasya's nose.

Mor... I mean, yes! - said Vasya, and Masha wrote down this answer on her piece of paper.

Yeah, - drawled Vasya's dad. He had been initiated into the order of the experiment, and now the four of them had finally finished calculating the results. A sheet of paper was drawn into two columns - in the left, all the correct answers were marked with chopsticks, and in the right, the wrong ones. - And how can we understand it?

Ten percent - this means that you did not feel anything and invented everything, - Masha said to Vasya.

But no, - Vasya's mother suddenly responded. - Vice versa. It means that you feel great. If you didn't feel anything, your answers would be somewhere around fifty percent, that's where all the accidents sit. And ten percent, just like ninety percent, cannot come from ignorance, from random answers. This figure is not random, it means something.

And what? Vasya asked gloomily.

I know! Masha suddenly exclaimed. - It means ... It means that you feel everything very well, but only the other way around! When there is no carrot, you are sure that it is, and when there is, that it is not!

For a couple of minutes everyone was silent, considering this discovery, and suddenly Vasya turned white.

So all the soups I've eaten... All the ones I've smelled like carrot-free, they're...

Vasya, - my mother frowned in pain, - I haven’t put carrots anywhere for a hundred years, I already have nightmares about carrots.

Vasya slowly turned his gaze to the plate of cold soup.

And there are no carrots here either, - my mother answered his silent question.

And by the way, you promised something! Masha said.

Okay, - Vasya slowly moved the plate and scooped up the first spoon.

Bon Appetit! Masha wished. - By the way, Aunt Marina! May I too? Another plate?

Insert for adults

The study of people's reactions to any impact, with the condition that the subjects are not initiated into the important details of the study. Method applied to exclude subjective factors, which can affect the result of the experiment.

double blind method- when not only the subjects, but also the experimenters do not know the important details of the experiment before its completion. The double - blind method eliminates the experimenter 's unconscious influence on the subject and the experimenter 's subjectivity in evaluating the results .

Blinding is often used in medical trials to avoid biased results due to the placebo effect, which occurs in 5-10% of patients (if not more often). However, the method does not exclude the subjective assessment of the patient's condition by the doctor conducting the study. Therefore, there is a need to “dazzle” the doctor as well [Wikipedia].

Blind method is an experimental method in which the subjects are not aware of what is being specifically studied. When the subject or experimenter can consciously or unconsciously influence the result, the blind method is mandatory.

For example, when conducting an expert evaluation of a project, the expert should not know who the proposal comes from, otherwise he may be guided by non-expert considerations. Further, the organizers of the tender can also influence the result by choosing a certain expert to evaluate a certain project, so it is important that this selection is also blind.

The blind method has become widespread in medical testing. To obtain objective results, patients are divided into two groups; one group receives the new drug and the other, the control group, receives placebo. At the same time, patients do not know which of them is in the control group. In this way, the so-called "placebo effect" is eliminated, which consists in the fact that the patient's condition may improve simply because he thinks he is taking an effective medicine. Although this method increases the objectivity of the study, it does not exclude the subjective assessment of the patient's condition by the doctor conducting the study. In the case of a double-blind method, the doctors directly involved in the trial also do not know which of the patients they are giving the medicine to and which placebo.

double blind method

The double-blind method lies in the fact that not only the subjects, but also the experimenters remain ignorant of the important details of the experiment until it is completed. The double-blind method eliminates the unconscious influence of the experimenter on the subject, as well as subjectivity in the evaluation by the experimenter of the results of the experiment.

The double-blind method is also used to scientifically test claims of paranormal abilities, such as the ability to read minds or determine the color of objects without the aid of sight ( skin-optical perception ).

As an example of how subjective factors can lead to a false interpretation of an experiment, one can cite the story of the discovery of the so-called. "N-rays", which was announced in 1903 by the French physicist Blondeau. N-rays, he said, enhanced the eye's ability to see dimly lit objects. He also claimed to have designed an N-ray spectroscope using an aluminum prism. Later, another physicist, Robert Wood, visited Blondeau's laboratory. Blondeau demonstrated his experiments to Wood and claimed that he was observing the action of rays on himself, despite the fact that Wood had quietly removed an aluminum prism from the spectroscope before the experiment.

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