1. A researcher conducts a randomized trial to determine the relationship between eating apples and visiting the doctor. The researcher finds that there is a positive relationship between these two events. Which of these is NOT a possible conclusion from this trial?

a) Eating apples leads to visiting the doctor.

b) Visiting the doctor leads to eating more apples.

c) Eating more apples and visiting the doctor have no correlation.

d) Some other factor causes people to both eat more apples and visit the doctor more often.

2. Why is a randomized trial the gold standard for solving the identification problem?