The November 17, 1994, issue of The New England Medical Journal reported on a study of the effects of hormone therapy on middle-aged women. About 750 women took part in the study; half were randomly selected to receive the hormone therapy, and the other half were given a placebo (they did not know which). After about a year, blood tests were conducted on each subject by a lab technician who was unaware of which group (treatment or placebo) the blood samples originated from. In presenting the results of the experiment, the authors reported that the women in the treatment group had experienced a statistically significant increase in HDL (the so-called "good" cholesterol) and a statistically significant reduction in LDL (the so-called "bad" cholesterol) when compared with the control group.

a) This is an example of a block design.
b) This is an example of a completely randomized design.
c) This is an example of a matched pairs design.
d) The treatments were the hormone therapy and the placebo.
e) The treatments were the HDL and the LDL.
f) The subjects are the 750 women in the study.
g) The subjects were the blood tests.
h) This study would be classified as un-blinded.
i) This study would be classified as single-blinded.
j) This study would be classified as double-blind.

The study involves 750 women as subjects and compares hormone therapy to a placebo in a double-blind setup to assess changes in cholesterol levels. Past observational studies wrongly suggested HRT's protective role in CVD, highlighting the need for rigorous trials to understand its true effects.

The study described is an example of how hormone replacement therapy (HRT) was researched in relation to its effects on cholesterol levels in middle-aged women. In this case, the subjects of the research are the 750 women who participated in the study, and the treatments administered were either hormone therapy or a placebo.

The research was designed as a double-blind experiment since both the participants and the lab technician assessing the outcomes were unaware of the group assignments. Such a study design is critical to eliminate biases and better establish a causal relationship between the intervention (HRT) and the outcomes (changes in HDL and LDL cholesterol levels).

The history of HRT and its association with risks and benefits, especially regarding cardiovascular disease and cancer, highlights the importance of well-designed randomized controlled trials over purely observational studies. A number of past studies incorrectly suggested that HRT reduced the risk of cardiovascular disease (CVD), but later, more carefully controlled trials refuted this and even showed potential adverse health outcomes.

Researchers continue to explore the complex role of HRT and its implications for women's health, stressing the importance of considering individual risks and benefits.

a) This is an example of a block design. - False

b) This is an example of a completely randomized design. - True

c) This is an example of a matched pairs design. - False

d) The treatments were the hormone therapy and the placebo. - True

e) The treatments were the HDL and the LDL. - False

f) The subjects are the 750 women in the study. - True

g) The subjects were the blood tests. - False

h) This study would be classified as un-blinded. - False

i) This study would be classified as single-blinded. - False

j) This study would be classified as double-blind. - True