Often, studies will refer to their design as “single-blind” or “double-blind.” As these are common phrases in science, you might think there is a standard definition for these terms. However, this is not the case.
You might think that “single-blinding” refers to the act of blinding patients, but in a 2001 survey of physicians and textbook language, 25% defined single blinding as the process of blinding someone other than the participants.
The same is true of the term “double-blind.” In the same study, only 40% of the physicians and textbooks defined this term as the act of blinding both the participants and the the treatment providers. The rest of those surveyed had various other definitions.
Because there is no consensus about the use of “single-blinding” and “double-blinding,” be wary of these terms and look for more detail when you evaluate this domain for risk of bias.
In fact, you may even see the term “triple-blind.” The possibilities are endless!
Let’s move on to the next domain for bias: a look at missing participant data.