Question 1

In the 1954 Salk vaccine experiment, which of the following best describes the role of the placebo group?

Accepted Answer

The placebo group received a harmless injection with no active vaccine to serve as a comparison for the treatment group.

Question 2

Which of the following is an example of a confounding variable in an observational study examining the relationship between ice cream sales and drownings?

Accepted Answer

Temperature, because it affects both ice cream sales and the likelihood of swimming.

Question 3

A researcher wants to select a sample of 100 students from a university of 10,000 students. She assigns each student a number and uses a random number generator to select the sample. What type of sampling is this?

Accepted Answer

Simple random sampling

Question 4

Which of the following best describes blinding in an experiment?

Accepted Answer

Blinding is when subjects do not know whether they are receiving the treatment or a placebo.

Question 5

A hospital administrator wants to survey patient satisfaction. She divides patients into groups based on the department they visited (e.g., cardiology, orthopedics, pediatrics), then randomly selects all patients from two of these departments to survey. What sampling method is this?

Accepted Answer

Cluster sampling

Question 6

Which of the following is a key difference between stratified sampling and cluster sampling?

Accepted Answer

Stratified sampling divides the population into subgroups and samples from each subgroup, while cluster sampling selects entire subgroups at random.

Question 7

A researcher wants to study the effect of a new drug. She randomly assigns 200 patients to receive the drug and 200 to receive a placebo. Neither the patients nor the doctors know who receives which treatment. What is this experimental design called?

Accepted Answer

Double-blind experiment

Question 8

Which of the following best defines a cross-sectional study?

Accepted Answer

A study in which data are collected at one point in time.

Question 9

In a systematic sample, which of the following procedures is most appropriate?

Accepted Answer

Select a random starting point and then select every $$kth $$individual from the population.

Question 10

A study follows a group of nurses over 20 years to observe the development of heart disease. What type of observational study is this?

Accepted Answer

Prospective (cohort or longitudinal) study

Question 11

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

Accepted Answer

Using a convenience sample instead of a random sample.

Question 12

A researcher wants to compare the effects of two diets. She matches subjects in pairs based on age and gender, then randomly assigns one in each pair to Diet A and the other to Diet B. What experimental design is this?

Accepted Answer

Matched pairs design

Question 13

Which of the following best describes replication in experimental design?

Accepted Answer

Repeating the experiment on more than one individual to observe variability in results.

Question 14

A study examines medical records from the past 10 years to determine the relationship between aspirin use and heart disease. What type of study is this?

Accepted Answer

Retrospective study

Question 15

Which of the following is a potential source of nonsampling error?

Accepted Answer

Data entry mistakes when recording survey responses.

Question 16

A researcher wants to ensure that both men and women are proportionally represented in a sample. She divides the population by gender and randomly samples from each group. What sampling method is this?

Accepted Answer

Stratified sampling

Question 17

Which of the following best describes the placebo effect?

Accepted Answer

An improvement in symptoms experienced by subjects who receive an inactive treatment.

Question 18

In a completely randomized experimental design, what is the primary method used to assign subjects to treatment groups?

Accepted Answer

Random selection

Question 19

A researcher selects the first student on a class list and then every 10th student thereafter to participate in a survey. What type of sampling is this?

Accepted Answer

Systematic sampling

Question 20

Which of the following statements about convenience sampling is true?

Accepted Answer

It often leads to biased results because the sample may not represent the population.

Sampling Methods and Experimental Design in Statistics

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