Question 1

Which of the following best describes a simple random sample?

Accepted Answer

A sample in which every possible sample of size $$n$$ has the same chance of being chosen.

Question 2

A pharmaceutical company wants to test a new drug. They randomly assign patients to receive either the drug or a placebo, and neither the patients nor the administering doctors know which group each patient is in. What type of experimental design is this?

Accepted Answer

Double-blind experiment

Question 3

Which of the following is an example of a lurking variable in the context of an observational study linking ice cream sales to drownings?

Accepted Answer

Temperature, because higher temperatures increase both ice cream sales and swimming activity.

Question 4

Which sampling method involves dividing the population into subgroups with similar characteristics and then randomly sampling from each subgroup?

Accepted Answer

Stratified sampling

Question 5

A researcher selects every 10th person entering a hospital to participate in a study. What type of sampling is this?

Accepted Answer

Systematic sampling

Question 6

Which of the following best defines a placebo?

Accepted Answer

A harmless and ineffective treatment used for psychological benefit or as a control in experiments.

Question 7

In which type of study are data collected from a past time period by examining records or interviews?

Accepted Answer

Retrospective (case-control) study

Question 8

A polling organization divides a city into neighborhoods, randomly selects several neighborhoods, and surveys every household in those neighborhoods. What sampling method is being used?

Accepted Answer

Cluster sampling

Question 9

Which of the following is a key reason why randomization is used in experimental design?

Accepted Answer

To create groups that are similar and reduce the impact of confounding variables.

Question 10

A study collects data on the blood pressure of patients at a single point in time. What type of observational study is this?

Accepted Answer

Cross-sectional study

Question 11

Which of the following is an example of a nonsampling error?

Accepted Answer

A researcher enters the wrong data into a spreadsheet.

Question 12

A hospital administrator wants to compare two treatments for infection. She matches patients in pairs based on age and severity, then randomly assigns one in each pair to each treatment. What design is this?

Accepted Answer

Matched pairs design

Question 13

Which of the following best describes confounding in an experiment?

Accepted Answer

When the effect of two or more variables cannot be distinguished from each other.

Question 14

A researcher uses a combination of stratified and cluster sampling in different stages of a national survey. What is this approach called?

Accepted Answer

Multistage sampling

Question 15

Which of the following is a characteristic of a randomized block design?

Accepted Answer

Subjects are grouped into blocks based on similar characteristics, and treatments are randomly assigned within each block.

Question 16

Which of the following is an example of a nonrandom sampling error?

Accepted Answer

Using a convenience sample instead of a random sample.

Question 17

A researcher wants to study the long-term effects of a new diet. She follows a group of participants for 10 years, collecting data at regular intervals. What type of study is this?

Accepted Answer

Prospective (cohort) study

Question 18

Which of the following statements about convenience sampling is true?

Accepted Answer

It often leads to biased results because the sample is not representative of the population.

Question 19

In an experiment, why is replication important?

Accepted Answer

It allows the effects of treatment to be observed across multiple subjects, increasing reliability.

Question 20

A researcher observes and measures the dietary habits of a group of people without attempting to change their behavior. What type of study is this?

Accepted Answer

Observational study

Introduction to Statistics: Data Collection and Experimental Design

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