If an Association Study Did Not Select People for the Study

Multiple Choice

If an association study did not select people for the study by using random sampling,which of the following statements is true?

A) The association should be rejected as inconclusive.
B) The variables should be measured more than once.
C) The effect size should be considered, but tests of statistical significance should not.
D) Moderators should be looked for.
E) None of the above statements are true.