Question 1

Which of the following best describes a simple random sample?

Accepted Answer

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

Question 2

In the context of the ice cream and drownings example, what is the lurking variable that explains the observed association?

Accepted Answer

The number of people swimming.

Question 3

Which sampling method involves dividing the population into subgroups and then randomly selecting members from each subgroup?

Accepted Answer

Stratified sampling

Question 4

A pharmaceutical company wants to test a new drug. They randomly assign subjects to receive either the drug or a placebo, and neither the subjects nor the administrators know who receives which. What type of experimental design is this?

Accepted Answer

Double-blind experiment

Question 5

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

Accepted Answer

Entering data incorrectly during analysis.

Question 6

What is the main difference between an observational study and an experiment?

Accepted Answer

An observational study observes and measures characteristics without attempting to modify the individuals, while an experiment applies a treatment and observes the effects.

Question 7

A researcher selects every 10th person entering a hospital for a survey. What type of sampling is this?

Accepted Answer

Systematic sampling

Question 8

Which of the following best describes replication in experimental design?

Accepted Answer

Repeating an experiment on more than one individual to ensure results are not due to chance.

Question 9

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

Accepted Answer

Multistage sampling

Question 10

Which of the following is a potential consequence of confounding in an experiment?

Accepted Answer

It prevents the researcher from identifying the specific factor that caused an observed effect.

Question 11

A study collects data from medical records of patients treated for heart disease over the past 10 years. What type of observational study is this?

Accepted Answer

Retrospective (case-control) study

Question 12

Which sampling method is most likely to result in a nonrandom sampling error?

Accepted Answer

Convenience sampling

Question 13

A researcher divides a population into men and women, then randomly selects subjects from each group. What type of sampling is this?

Accepted Answer

Stratified sampling

Question 14

Which of the following is NOT a method for controlling the effects of variables in an experiment?

Accepted Answer

Convenience sampling

Question 15

A study measures cholesterol levels in a group of adults at a single point in time. What type of observational study is this?

Accepted Answer

Cross-sectional study

Question 16

Which of the following best describes a placebo?

Accepted Answer

A harmless and ineffective pill, medicine, or procedure used for psychological benefit or comparison in experiments.

Question 17

A researcher randomly selects several schools and surveys all students in those schools. What sampling method is being used?

Accepted Answer

Cluster sampling

Question 18

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

Accepted Answer

To use chance as a way to create groups that are similar.

Question 19

A study follows a group of smokers and non-smokers for 20 years to observe the development of lung disease. What type of observational study is this?

Accepted Answer

Prospective (cohort) study

Question 20

Which of the following is the correct formula for the probability of selecting a specific sample in a simple random sample of size $$n$$ from a population of size $$N$$?

Accepted Answer

$$\frac{1}{\binom{N}{n}}$$

Introduction to Statistics: Collecting Sample Data and Experimental Design

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