There is a problem:
Which of the following sources of bias is eliminated by randomization?
a) Researchers have a desired outcome in mind
b)certain groups are systematically excluded from the data
c) Certain groups are categorically exclded from the data
d)people with strong opinions are counted before others
e)some groups are aware of the reason for the data search
I think, that answers b) and c) are right, but I don't know which one to choose. Can you help me?
Thank you very much!