In a study, a large sample representative of the female population in the US were asked whether they take oral contraceptives. The data suggests that users of oral contraceptives have a higher rate of cervical than non-users even after adjusting for age, education and marital status. Investigators concluded that the pill causes cervical cancer. Consider the following statements.

Please select ALL the choices you agree with, based on the information given.

A) This study is a randomized controlled experiment.

B) This is an observational study.

C) The results can be explained due to confounding. Women using the pill are different from non-users in ways that are related to higher frequency of cervical cancer.

D) In a randomized experiment, user and non-user groups are similar across all potential characteristics.

E) The conclusions were justified by the data.