Question

the use of blind or double-blind investigators in a study is done to avoid:

sampling error.

sample bias.

uncontrollable variables.

researcher bias.

random error.

i think it is researcher bias

Answer 1

Didn't you understand bobpursley's answer?

https://www.jiskha.com/questions/1774701/The-use-of-blind-or-double-blind-investigators-in-a-study-is-done-to-avoid-sampling

Answer 2

Possibly you might understand this explanation.

1. <B>Single blind</B> gives the control group a <B>placebo</B> — a substance that is inert, it has no physical effect. Subjects don't know if they are in experimental or control group to reduce placebo effect, a change in behavior solely due to believing that you are getting the independent variable.

2. <B>Double blind</B> keeps both subjects and experimenter ignorant of group setup. Distribution of the independent variable and placebo are controlled by third party. This controls for experimenter bias and <B>self-fulfilling prophecy</B>, which means that experimenters with particular expectations are likely to consciously or unconsciously to bias the experiment and influence it to conform to their expectations.