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wargarbleEleventyTen t1_jduueop wrote

The people conducting the study. One team ( could be one person, I suppose ) does the blinding and other people do the treatment and data collection. Data analysis happens on blinded data but you can always unblind, during the study, if something goes wrong, otherwise at the end.

It is or at least was considered good form to give the control group access to the treatment after the study, if it was successful.


dkppkd OP t1_jdvaoft wrote

Can we really trust members of the same team or even same organization? I consider myself an honest person, but unconscious biases can easily slip in, especially under pressure and lack of sleep.


ScienceIsSexy420 t1_jdvcw3f wrote

No system is perfect, and it's practically impossible to entirely prevent bad actors from circumnavigating safety precautions. However, researchers are aware that maintaining the double blind nature of the study is necessary to properly evaluate medical outcomes, and we do everything possible to ensure the quality of our research is unadulterated. Think of it this way: why would we want to invalidate years of work?


h3rbi74 t1_jdw7iae wrote

The point of the double blinding is specifically to counteract the unconscious biases that may occur in a single blind trial, but it can’t always be proof against someone very consciously trying to circumvent the system.

Let’s say you have a single-blind trial of a new pain killer for example. The subject doesn’t know if they are getting the new drug being investigated, an old drug that’s the usual treatment, or a placebo. But because it’s NOT double blind, the researcher DOES know which bottle contained which medication and which patient gets each one. Now even if he tries really hard to be objective and impartial, he might accidentally rate one group as limping less on the treatment he thinks is going to work best, or he might avoid giving the placebo to someone he feels sorry for and wants to make sure is getting a real treatment, and accidentally skew the groups so it’s not a fair comparison.

If the same experiment were run as a double-blind experiment, one researcher or team will divide the participants into randomized groups and pass out the medication— and if at all possible that medication will be formulated to appear identical (each dose is 2 capsules of the same size and color, for example, no matter what’s inside them), and once they’ve told the participants the instructions for how to take the meds and what surveys to fill out to track their progress and when they need to come back for rechecks with the doctor(s), they’re done for now. An entirely different researcher or team will actually collect the data, and they will have absolutely no idea who is getting what. So in order to fudge the results they would need to break into the other team’s files and sneak a peek at the list of who got what, but that’s deliberate cheating at that point, not unconscious bias.

However: you’re not wrong that— like life in general— there are a LOT of ways very subtle unconscious bias can slip into the process (who gets recruited for the study, for example— do you only advertise in certain neighborhoods? In certain languages? And so on…) I just did a search for “experimental design to avoid bias” and there was no one particular great link to point you at because there were MANY resources and webinars and publications, meant to train university and medical researchers and also to look back and evaluate any bias that might only be obvious in hindsight, the better to avoid it in future.


dkppkd OP t1_jdwd716 wrote

Thanks for the detailed answer. I appreciate the real-world example which clears up some misconceptions.


Electronic_Health22 t1_je330eq wrote

Maybe in the past, but now it's all handled by computers that can do this relatively easily.


[deleted] t1_jdunkeg wrote



wargarbleEleventyTen t1_jduu65e wrote

That goes a bit far, though it may happen with some specific experiment is psychology.

Otherwise double blind means that neither the person getting the treatment nor the people administering it and collecting data know, if the subject is part of the treatment or the control arm.

Generally everyone knows what the study is about. Bit hard to keep that secret, really.


Brain_Hawk t1_jduukr7 wrote

Part that's missing in the above answer is that the original research was usually blinded. Typically a third person who is not involved in data collection or analysis is the one who was aware of the group labels.

To do properly, during the initial statistical analysis to groups are also done blinded. For example you label them groups a, b, c. Only after you have performed statistical analysis of the effects of the intervention, for example, then do you afterwards get to unblind

So it can happen you have what looks like a very nice effect, and then realize that it's the placebo group we got better! I've seen it happen :p


wargarbleEleventyTen t1_jduvobv wrote

Oh definitely. I could have been clearer in the comment. The person(s) doing the assignment are not involved in either the data collection nor the analysis.

Everyone else does not know, what branch a subject is in, until the study is over. If something serious happens you can of course unblind immediately.


rootofallworlds t1_jduxppr wrote

This doesn't seem right, not in all cases anyway.

In most clinical trials the patient knows that it's a clinical trial, what condition is being treated, and that they will be randomly given either the treatment or a placebo. It would be unethical for the participants to not know that.

You seem to be thinking of psychology studies, where it is commonplace to tell subjects and workers a study is about one thing when really it's about another.


ZZ9ZA t1_jdykcq0 wrote

It’s not always a placebo, either. It’s my understanding that in testing of things like pain killers the control is often something like a benzodiazepine just because the patient understands that they are likely to feel relaxed/sleepy and a true placebo would essentially unblind the study.


YesWeHaveNoTomatoes t1_jdv5lis wrote

>A blind study has a researcher doing something with a subject that is not aware of the study's true / detailled aim.
>A double blind study has a researcher tasking another researcher to do something with a subject, with neither the subject nor the tasked researcher knowing what the study is actually about.

This is not correct and would violate principles of informed consent. A blind study is one in which the participant doesn't know if they are getting the the study drug (or procedure or whatever) or if they're getting a placebo. A double-blind study is one in which the participant and the tasked researcher both don't know whether the participant is getting the drug or the placebo. In all cases the participant must know what the purpose of the drug is and any negative effects taking it or not taking it may have.


JonJackjon t1_jdywjaf wrote

The concept is simple.

Person 1 marks the test samples in some random order, recording the markings.

Person 1 leaves the room

Person 2 takes the samples and gives them to the test subjects, recording which goes to whom.

After the results are logged and maybe even analyzed, the information from person 1 is used to "decode" which sample went to whom.


Ok-Arm-362 t1_jdyyfya wrote

How it actually works for most studies for meds. We get shipped a bunch of identical boxes - identical except some contain placebo, some investigational product. After the potential subject passes the screening process (to ensure they are a good candidate and meet all inclusion criteria), we log into a program that gives us the code number for the box to give the subject. The distribution of numbers is predetermined. No one really knows what is distributed.

FWIW, fraud - if it exists - has nothing to do with the desired outcome. It is the result of the financial motivation to enroll subjects, which can be significant. Most of the unsavory activity is from greedy sites enrolling unqualified or even phony people.


dkppkd OP t1_jdz50p3 wrote

This is the answer i was looking for. Is there a type of company or organization in charge of labeling these boxes and keeping the secret or is this just another group within your organization?


Ok-Arm-362 t1_je0hdr6 wrote

Glad it helps. Actually, many more layers of separation than you imagine for clinical trials. (And many variations on how randomization is achieved). Most trials have dozens of independent locations that have little to connection with each other. Typically, the pharmaceutical company contracts with a 'clinical research organization' (CRO) to coordinate it all. The CRO usually uses a separate system and/or company to perform randomization. And the whole thing is potentially monitored by yet another separate agency and subject to legal scrutiny and penalties for wrongdoing by the FDA. You can find more deets at have fun 👍


flashmeterred t1_jdyg0u9 wrote

usually one/two are in charge of anonymising the treatment. The fewer, the better to keep things clearer. They will track how they've anonymised it, store that information elsewhere, and then destroy evidence used during the process (like any quick notes made during).

Other researchers then perform the actual experiment/trial and track the anonymised notation (symbols/letters/numbers) with the experimental info.

You have to remember, the anonymisation is only being performed at the behest of THE RESEARCHERS. THEY (or bodies related to the researchers) want to know that A works and B does not, because every dead end cut off early is money saved. They're not going to circumvent their own process for... no apparent gain (unless they are a biotech startup with unrealistic goals in Silicon Valley happy to fake real patient data, I guess... thats another story).

That said... sometimes the immediate observable results kind of give away which treatment might be which, so its not always avoidable.


Electronic_Health22 t1_je32xsj wrote

There is somebody, usually the trial coordinator who takes care of the randomization and the linking of the randomization card to the patient. In the modern era, the computer "knows" who is assigned to what without necessitating a human to know.