Question

6 in an experiment, subjects are put into two categories according to sex, and then each subject is randomly assigned a treatment. this is an example of... a randomize blocking b gender bias c confounding d observational studies

Explanation:

Blocking groups subjects by a characteristic (here, sex) then randomly assigns treatments within each group, which matches the experiment described. Gender bias refers to unfair preference, confounding is a hidden variable affecting results, and observational studies do not assign treatments.

Answer:

A. randomize blocking