Question 1

A pharmaceutical company wants to test a new drug for reducing blood pressure. They randomly assign 500 patients to receive the drug and 500 to receive a placebo, then compare the results. Which type of study is this, and what is the main advantage of this design?

Accepted Answer

Experiment; it allows for control of confounding variables and can establish causality.

Question 2

Which of the following best describes a stratified sampling technique?

Accepted Answer

Dividing the population into groups based on a characteristic, then randomly sampling from each group.

Question 3

A researcher wants to study the effect of a new teaching method on student performance. She pairs students based on their previous test scores, then randomly assigns one from each pair to the new method and the other to the traditional method. What experimental design is being used?

Accepted Answer

Matched-pairs design

Question 4

Which of the following is an example of a confounding variable in an experiment testing a new diet's effect on weight loss?

Accepted Answer

Participants' exercise habits during the study

Question 5

A city government wants to estimate the average household income. They divide the city into zip codes and randomly select all households in three zip codes to survey. Which sampling method is this?

Accepted Answer

Cluster sampling

Question 6

In a double-blind experiment, who is unaware of which subjects are receiving the treatment?

Accepted Answer

Both the subjects and the experimenters

Question 7

A researcher uses a computer to randomly select 50 students from a list of all 2,000 students at a university. What type of sampling is this?

Accepted Answer

Simple random sampling

Question 8

Which of the following best describes the placebo effect?

Accepted Answer

A subject experiences a real response after receiving a fake treatment.

Question 9

A car manufacturer uses computer models to study the effects of crashes on human bodies. What data collection method is being used?

Accepted Answer

Simulation

Question 10

A researcher wants to study the opinions of all students at a university about a new policy. She stands outside the library and surveys the first 100 students who walk by. What is the main problem with this sampling method?

Accepted Answer

It is a convenience sample and may not be representative of the entire student population.

Question 11

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

Accepted Answer

Control, randomization, and replication

Question 12

A researcher wants to select a sample of households from a city. She randomly chooses a starting point and then selects every 50th household on the list. What sampling method is this?

Accepted Answer

Systematic sampling

Question 13

A study is conducted to determine how confident Americans are in the economy by calling 3,040 adults and asking them to rate current economic conditions. What type of study is this?

Accepted Answer

Observational study

Question 14

Which of the following scenarios best illustrates a sampling error?

Accepted Answer

The average income calculated from a sample differs from the true average income of the population.

Question 15

A company tests a new gum to help people quit smoking by giving it to five heavy smokers and a placebo to another five. After two months, all five using the gum have quit. What is the main flaw in this experiment?

Accepted Answer

The sample size is too small to validate the results.

Question 16

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

Accepted Answer

$$P = \frac{1}{N}$$

Question 17

A researcher divides a population of households into three income levels (low, middle, high) and randomly selects households from each level. What is the main benefit of this sampling method?

Accepted Answer

It ensures that all income levels are represented in the sample.

Question 18

In a randomized block design, what is the purpose of dividing subjects into blocks before random assignment?

Accepted Answer

To control for variables that could affect the outcome by grouping similar subjects together.

Question 19

A survey is conducted by mailing questionnaires to a random sample of 1,000 people. What is a potential source of bias in this method?

Accepted Answer

Nonresponse bias, since people who do not return the questionnaire may differ from those who do.

Introduction to Data Collection and Experimental Design in Statistics

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