Blind Procedures

Individuals can enter into studies with biases that skew results, portraying a treatment as being more effective than it actually is.

For instance, during an insomnia study, a researcher may place a sleep-aid or placebo tablet in a cup, and disperse the capsules to participants. While the scientist notes who received which type of pill, subjects are oblivious.

Here, the researcher remains biased, anticipating that the sleep-aid will work. Thus, during observation, she may note that those administered the drug fell asleep faster, while in reality there is no difference between groups.

However, participant biases are eliminated. Since subjects don't know if they swallowed the sleep-aid, they lack expectations regarding the efficacy of the pill. Consequently, they’ll accurately state how their insomnia was affected.


This method, where only researchers or participants realize who obtained treatment, is termed a single-blind study. However, this procedure can result in one group—here, the scientist—remaining biased.

To circumvent this, double-blind studies are performed, where both participants and the data-collecting researchers are “blind”. Here, the scientist may give the placebo and sleep-aid to a colleague, who re-labels the pills as “Type Y” and “Type Z” before dispersing them.

This coding system eliminates the researcher’s expectations during assessment—she doesn’t know which participants received the medication, and can’t assume who should sleep better. Consequently, she’ll record if someone appears restless.

As before, subjects will also precisely describe their sleep experience. It’s only after data analysis that everyone learns who was administered the sleep-aid or placebo.

Overall, blind procedures help to minimize biases and produce accurate results, which can be used to assess the efficacy of medication and other treatments.