Question 1

Which of the following best describes the difference between an experiment and an observational study?

Accepted Answer

In an experiment, researchers determine which individuals are in the treatment and control groups, often by using random assignment.

Question 2

A researcher wants to test if a new medication reduces blood pressure. She randomly assigns 100 patients to receive the medication and 100 to receive a sugar pill. Neither the patients nor the staff know who receives which pill. What type of study is this?

Accepted Answer

Double-blind experiment

Question 3

Which of the following is a key component of a well-designed experiment?

Accepted Answer

Using a control group and at least one treatment group

Question 4

What is the main purpose of random assignment in an experiment?

Accepted Answer

To reduce the impact of lurking and confounding variables

Question 5

In a study, $$x is $$the amount of exercise per week and $$y is $$the cholesterol level. Which is the explanatory variable?

Accepted Answer

$$x$$, amount of exercise per week

Question 6

A lurking variable is best described as:

Accepted Answer

A variable that causes both the explanatory and response variables to change during the study

Question 7

Which of the following scenarios best illustrates the placebo effect?

Accepted Answer

A patient’s symptoms improve after taking a sugar pill, believing it is real medication

Question 8

Why can most observational studies not determine causality?

Accepted Answer

They do not use random assignment

Question 9

A confounding variable is:

Accepted Answer

A variable other than the explanatory variable that causes or helps cause the response variable to change during the study

Question 10

In a study, researchers want to know if a new teaching method improves test scores. They let students choose which method they want to use. What is a major flaw in this design?

Accepted Answer

There is no random assignment, so groups may differ in important ways

Question 11

Which of the following best describes a single-blind study?

Accepted Answer

The individuals do not know whether they are in the treatment or control group

Question 12

A researcher wants to test if vitamin D supplements reduce the risk of colds. She randomly assigns 200 people to receive either vitamin D or a placebo, and neither the participants nor the staff know who receives which. What is the explanatory variable?

Accepted Answer

Whether the participant receives vitamin D or placebo

Question 13

Which of the following is NOT a component of a well-designed study?

Accepted Answer

Allowing participants to choose their group

Question 14

A study finds that people who exercise regularly have lower rates of heart disease. Which of the following is a possible lurking variable?

Accepted Answer

Genetic predisposition to heart disease

Question 15

In a study, $$x is $$the amount of sleep per night and $$y is $$the number of sick days per year. Which is the response variable?

Accepted Answer

$$y$$, number of sick days per year

Question 16

A researcher wants to redesign an observational study about vitamin C and colds into a well-designed experiment. Which of the following changes would improve the study?

Accepted Answer

Randomly assigning participants to treatment and control groups and using a placebo

Question 17

Which of the following best explains why a double-blind study is preferred over a single-blind study?

Accepted Answer

It prevents both participant and researcher bias

Question 18

A study finds an association between eating breakfast and higher test scores. Why can’t we conclude that eating breakfast causes higher test scores?

Accepted Answer

There may be lurking or confounding variables, and observational studies cannot determine causality

Question 19

Which of the following is an example of response bias in a study?

Accepted Answer

Participants forget to report some instances of illness

Question 20

In a study, researchers want to know if a new fertilizer increases crop yield. They randomly assign fields to receive the fertilizer or not, and compare yields. What is the response variable?

Accepted Answer

The crop yield

Designing Observational Studies and Experiments

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