Author Topic: None So Double Blind  (Read 5209 times)

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Offline Jack Mann

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None So Double Blind
« on: January 18, 2012, 05:33:14 am »
So, let's talk about double blind tests for a moment.

This is one of those things that a lot of people have trouble understanding.  Even people who remember how the scientific method works often don't understand what double blind tests are, or how and why they're used.

First off, let's talk about what double blinds are.  At the most basic, a double blind experiment is one where neither the subjects of the experiment, nor the ones directly administering the experiment, know the exact details of the experiment.  So, while someone sets up the experiment, and knows what each group in the experiment is doing, they don't interact with the subjects.

Now, they're not used for every experiment.  You'll notice I mentioned "subjects."  Double blinds are typically used when experimenting on people, or when people can affect the results of the experiment without realizing it.  How can that happen?  And how can double blinds stop it from happening?

Drug trials are a good example of this sort of experiment.  Just being told they're taking a medicine can help people feel better, which is what we call the placebo effect.  Because of that, it can be difficult to tell if a drug's actually had an effect, or if the person just felt better for thinking it was.

Similarly, tests for psychic abilities (like dowsing or reading minds) can be affected.  Obviously, if the subject knows where the water or gold is hidden beforehand, they're going to focus on that object.  Even if they're not consciously aware that they're doing so, they can still do it without realizing it.

And moreover, perceptive subjects can pick up on the reactions of those administering the tests.  In the drug trials, they might be able to tell if they're really being given a drug or not.  In a test of psychic abilities, the psychic might pick it up from the faces of those testing them, seeing if they're tensing up as they get near the object.

So, we withhold that information from everyone present at the test.  This is why it's called a "double" blind, as opposed to a single blind, when only subjects are kept in the dark.  Even the ones who are directly administering the test aren't aware of who's in the control group, or where things are.  That way, the drug and the placebo are competing on equal ground, and the drug has to do significantly better than the placebo to be declared effective.  The psychic has to beat random chance with no clues available before he can be taken seriously.

Double blinds are there to reduce as many extraneous factors from the experiment as possible, so that only the factor you're testing for--drug efficacy, dowsing, or dog food taste--is actually being tested.  A double blind is much more accurate, and much harder to argue with than a single blind or no blind test.
« Last Edit: January 18, 2012, 07:20:58 pm by Jack Mann »
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Offline The Right Honourable Mlle Antéchrist

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Re: None So Double Blind
« Reply #1 on: January 18, 2012, 09:56:04 am »
Well said. :)
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Offline Lithp

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Re: None So Double Blind
« Reply #2 on: January 18, 2012, 10:04:42 pm »
Where were you about 5 months ago?

Offline Radiation

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Re: None So Double Blind
« Reply #3 on: January 20, 2012, 01:56:35 pm »
This is a nice and concise explanation of the double blind study. I remember reading about it in my psychology book and being confused but you cleared it up.
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Offline rosenewock21

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Re: None So Double Blind
« Reply #4 on: January 21, 2012, 10:07:25 am »
Perhaps this should be sticky'd? It seems like such useful information to let it get lost in the back pages.
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Offline Yla

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Re: None So Double Blind
« Reply #5 on: January 22, 2012, 09:34:04 am »
Can you explain how a triple blind study works then? Even the evaluators aren't in the know in these, but then how do you get a result?
That said, I've stopped trying to anticipate what people around here want a while ago, I've found it makes things smoother.
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Offline Jack Mann

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Re: None So Double Blind
« Reply #6 on: January 22, 2012, 01:57:22 pm »
As you said, the evaluators don't know.  However, that doesn't mean the information isn't kept.  For example, there might be someone else who isn't monitoring the experiment, but has kept the information.  Or it might have been randomized, but in such a way as to make sure the information can be recovered later (via a computer, perhaps).  It's just another layer of security to keep expectations from affecting the data.
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