Question 1

Which of the following best describes a confounding variable in an observational study?

Accepted Answer

A variable that is associated with both the explanatory and response variables, making it difficult to distinguish their individual effects.

Question 2

In a study investigating the effect of a new antihypertensive drug, patients are randomly assigned to receive either the new drug or an existing drug. What type of study is this?

Accepted Answer

Experiment

Question 3

Which of the following statements about randomization in experiments is TRUE?

Accepted Answer

Randomization helps to average out the effects of extraneous variables across treatment groups.

Question 4

A researcher wants to study the effect of diet and exercise on weight loss. Participants are randomly assigned to one of four groups: (1) diet only, (2) exercise only, (3) both diet and exercise, (4) neither. What type of experimental design is this?

Accepted Answer

Completely randomized design with two factors

Question 5

Which of the following is an example of a lurking variable?

Accepted Answer

In a study of firefighters and fire damage, the size of the blaze affects both the number of firefighters sent and the amount of damage.

Question 6

What is the main purpose of using a placebo in an experiment?

Accepted Answer

To blind the experimental units so that their response is not influenced by knowing their treatment assignment.

Question 7

In a randomized block design, which of the following is TRUE?

Accepted Answer

Experimental units are first divided into blocks based on a variable believed to influence the response, and then treatments are randomly assigned within each block.

Question 8

Which of the following best describes a double-blind experiment?

Accepted Answer

Neither the experimental units nor the evaluators know which treatment the units are receiving.

Question 9

Suppose a study finds that students who take music lessons have higher grades, but students who take music lessons also tend to come from wealthier families who can afford private tutors. What is the role of private tutoring in this scenario?

Accepted Answer

It is a confounding variable.

Question 10

Which of the following is NOT a principle of experimental design?

Accepted Answer

Stratification

Question 11

A study follows a group of individuals over several years to observe whether they develop a certain disease. What type of study is this?

Accepted Answer

Prospective study

Question 12

In a matched pairs design, which of the following is TRUE?

Accepted Answer

Subjects are paired based on similar characteristics, and each pair is randomly assigned to different treatments.

Question 13

Which of the following statements about statistical significance is correct?

Accepted Answer

A difference is statistically significant if it is larger than what would be expected by chance alone.

Question 14

Which of the following best distinguishes a factor from a blocking variable in experimental design?

Accepted Answer

A factor is a variable whose effect on the response is of interest and is manipulated, while a blocking variable is used to control for variation but is not of primary interest.

Question 15

In the context of the antihypertensive drug experiment, which of the following would be an appropriate blocking variable?

Accepted Answer

Gender of the patients

Question 16

Which of the following scenarios is most likely to result in confounding?

Accepted Answer

Assigning students to web-based or traditional courses based on the term (summer or winter) in which the course is offered.

Question 17

Which of the following is a key difference between an observational study and an experiment?

Accepted Answer

In an experiment, the researcher manipulates the explanatory variable, while in an observational study, the researcher does not intervene.

Question 18

Suppose in a clinical trial, the observed effect of a new drug is similar to the effect observed in the placebo group. What is the most reasonable conclusion?

Accepted Answer

The observed effect is likely due to the placebo effect rather than the drug itself.

Question 19

Which of the following best describes a retrospective study?

Accepted Answer

A study in which individuals are first identified based on exposure and then their past outcomes are examined.

Question 20

In the context of experimental design, what is the main reason for replication?

Accepted Answer

To ensure that the results are not due to chance and can be generalized to a broader population.

Experiments and Observational Studies: Design, Comparison, and Interpretation

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