Question 1

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

Accepted Answer

An observational study observes subjects without intervention, while an experiment assigns treatments to subjects and observes outcomes.

Question 2

A researcher wants to study the effect of a new fertilizer on plant growth. She randomly assigns 50 plants to receive the new fertilizer and 50 plants to receive no fertilizer, then measures their growth after 8 weeks. What type of study is this?

Accepted Answer

Experiment

Question 3

In a Gallup poll, 1,015 adults were randomly selected from all 50 U.S. states and the District of Columbia. The poll reported that 43% of respondents were satisfied with K-12 education. In this context, what is the implied population?

Accepted Answer

All U.S. adults

Question 4

Which of the following is a potential source of bias in sample surveys?

Accepted Answer

Nonresponse

Question 5

Suppose you want to estimate the average commute time for all employees at a large company. You select every 10th employee from an alphabetical list. What type of sampling method is this?

Accepted Answer

Systematic sampling

Question 6

Which of the following statements about cluster sampling is TRUE?

Accepted Answer

Cluster sampling is less expensive when the population is geographically spread out.

Question 7

A study divides participants into men and women, then randomly selects 50 men and 40 women to participate. What type of sampling is this?

Accepted Answer

Stratified random sampling

Question 8

Which of the following best describes the placebo effect?

Accepted Answer

The response of a patient to any treatment, even a dummy treatment, because of trust and expectations.

Question 9

In a completely randomized experimental design, what is the main purpose of randomization?

Accepted Answer

To balance the groups with respect to both known and unknown lurking variables.

Question 10

Which of the following is an example of response bias?

Accepted Answer

Respondents underreporting illegal drug use on a survey.

Question 11

A researcher wants to compare the effectiveness of three advertisements. She randomly assigns men and women separately to view one of the three ads. What type of experimental design is this?

Accepted Answer

Block design

Question 12

Which of the following is a key advantage of stratified random sampling?

Accepted Answer

It ensures enough subjects in each group you want to compare.

Question 13

Suppose a study follows a group of people over 10 years to see who develops heart disease. What type of study is this?

Accepted Answer

Prospective (cohort) study

Question 14

Which of the following is a reason why a researcher might choose an observational study over an experiment?

Accepted Answer

For ethical or practical reasons

Question 15

A study selects a random sample of city blocks, then surveys every household within those blocks. What type of sampling is this?

Accepted Answer

Cluster sampling

Question 16

Which of the following is TRUE about the relationship between sample size and bias?

Accepted Answer

A large random sample gives more accurate results, but a large biased sample is still biased.

Question 17

In a matched pairs design, what is the main advantage?

Accepted Answer

It uses pairs of subjects that are closely matched, reducing the effect of lurking variables.

Question 18

Which of the following best describes undercoverage?

Accepted Answer

When some groups in the population are left out of the process of choosing the sample.

Question 19

Suppose a study asks, 'Do you agree that the government should not reduce funding for education?' What type of bias might this question introduce?

Accepted Answer

Response bias due to wording effects

Question 20

Which of the following is a key principle of experimental design?

Accepted Answer

Replication

Chapter 4: Gathering Data – Study Notes for Statistics Students

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