Study biases and confounding would affect the _______ validity of a study. 

A) External

B) Internal 

Randomized controlled trials (RCTs) are the strongest research design for establishing cause and effect. Which of the following is the main limitation of RCTs?

a) RCTs may not be ethical for some studies.

b) RCT design cannot control for confounders.

c) Randomized controlled trials may have a disproportionate number of people exposed to the risk factor.

d) Randomized controlled trials are, by their very design, likely to be very biased towards an expected outcome.

Learning Station 1: Plant Structure for Photosynthesis Label the internal parts of the leaves. Choose the word from the box. Then, write your choice inside the box of Figure 1.

In a small study, 12 women with cervical cancer (cancer of the cervix) and 12 women with no apparent cervical cancer were contacted and asked whether they had ever used the hormone estrogen as a drug. Each woman with cancer was matched by age, race, and weight with a woman without the disease. This is an example of:

a) A randomized controlled trial

b)A prospective cohort study

c) A case-control study

d) A retrospective cohort study