Question

A scientist is studying the effects of cell phone use on headache rate. She identifies 30 people who use cell phones and 30 who do not. Each of the 60 people is given a questionnaire designed to determine headache frequency. None of the 60 people who participated in the study knew they were part of a study. Which statement is true?

Answer 1

C this is a double blind study.

Explanation:

Both groups in the experiment are blind (don't know they are in an experiment). If this answer is incorrect then its A.

Answer 2

observational study

Explanation:
the experimenters are not blind to their own tests.