Question 1

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

Accepted Answer

A variable that is associated with both the explanatory and response variables, making it difficult to determine the true effect of the explanatory variable.

Question 2

A study finds a strong association between the number of televisions in a household and the life expectancy of its residents. Which of the following is the most likely explanation for this association?

Accepted Answer

A lurking variable, such as economic status, is associated with both the number of televisions and life expectancy.

Question 3

Which of the following is NOT one of the four principles of experimental design?

Accepted Answer

Select only participants who are likely to respond positively to the treatment.

Question 4

In a double-blind experiment, who is unaware of which subjects receive which treatments?

Accepted Answer

Both the subjects and all who evaluate the results.

Question 5

A researcher wants to study the effect of a new fertilizer on plant growth. She randomly assigns 100 plants to receive the new fertilizer and 100 plants to receive no fertilizer. She measures the height of each plant after 8 weeks. Which principle of experimental design is illustrated by randomly assigning plants to treatments?

Accepted Answer

Randomization

Question 6

Which of the following best describes a retrospective observational study?

Accepted Answer

A study that looks at an outcome in the present and searches for past factors that may be related.

Question 7

Why is randomization important in experimental design?

Accepted Answer

It balances confounding variables across treatment groups on average.

Question 8

A pharmaceutical company tests a new drug by giving it to one group and a placebo to another. Neither the patients nor the doctors know who receives the drug. What type of study is this?

Accepted Answer

Double-blind experiment

Question 9

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

Accepted Answer

Experiments randomize treatments to subjects, while surveys aim for a representative random sample.

Question 10

Suppose a study finds a positive association between ice cream sales and murder rates. Which of the following is the best explanation?

Accepted Answer

A lurking variable, such as weather, is associated with both ice cream sales and murder rates.

Question 11

Which of the following is an example of blocking in an experiment?

Accepted Answer

Grouping subjects by age before randomly assigning treatments within each group.

Question 12

A researcher records the temperature during an experiment, even though it was not originally a factor. Later, she finds that temperature affected the results. What statistical practice does this illustrate?

Accepted Answer

Recording additional information to help in analysis and control for confounding variables.

Question 13

Which of the following is a necessary condition to establish causation in a study?

Accepted Answer

A carefully designed experiment where the cause precedes the effect.

Question 14

A bank sends out two types of credit card offers and finds more people sign up for the low-rate/no-fee card. What issue might affect the validity of this conclusion?

Accepted Answer

Confounding

Question 15

Which of the following best describes a control group in an experiment?

Accepted Answer

A group that receives a placebo or null treatment to mimic the treatment being studied.

Question 16

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

Accepted Answer

A variable that is associated with both the explanatory and response variables, but is not included in the study.

Question 17

Which of the following is a recommended practice when designing an experiment?

Accepted Answer

Try a small pilot run first, then refine the study before the full-scale experiment.

Question 18

Which formula would you use to calculate the average response in a treatment group?

Accepted Answer

$$	ext{Average} = \frac{\sum_{i=1}^{n} x_i}{n}$$

Question 19

Which of the following best describes replication in experimental design?

Accepted Answer

Applying each treatment to more than one participant.

Confounding, Lurking Variables, and Experimental Design in Statistics

Study Guide - Practice Questions

Study Guide - Flashcards