Answer
Experimenter bias arises at the possibility that the observer might consciously or subconsciously interpret test results to their own favour. Double-blind method secures the objectivity of a test, as both the observer and participant are unaware of which portion is placebo.
Statistical estimation bias arises when the estimated outcome value differs noticeably from the actual outcome. To prevent inaccuracy there are special statistical tests that assist in analysing the data. Examples would be the chi-square test, t test, and analysis of variance.
Work Step by Step
The examples I gave on bias were described in the text "Experimental design", even though there are more types of bias one can look up; I summarized my two choices in the way that seemed simple and clear for an answer.
