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, but the researchers know which group each patient is in, while the patients do not. What type of experimental design is this?

Accepted Answer

A single-blind experiment

Question 2

Which of the following best describes a stratified sampling technique?

Accepted Answer

Dividing the population into strata based on a characteristic, then randomly selecting some members from each stratum

Question 3

A researcher wants to estimate the average commute time for employees at a large company. She assigns each employee a number, randomly selects a starting number, and then surveys every 10th employee. What sampling method is being used?

Accepted Answer

Systematic sampling

Question 4

In an experiment, a confounding variable is:

Accepted Answer

A variable that cannot be distinguished from the effects of the treatment on the response variable

Question 5

A study is conducted to determine whether a new teaching method improves student performance. Students are paired based on their previous test scores, and within each pair, one is randomly assigned to the new method and the other to the traditional method. What type of experimental design is this?

Accepted Answer

Matched-pairs design

Question 6

Which of the following is a key difference between an observational study and an experiment?

Accepted Answer

An experiment applies a treatment to subjects, while an observational study does not

Question 7

A city is divided into 20 neighborhoods. To estimate average household income, a researcher randomly selects 4 neighborhoods and surveys every household in those neighborhoods. What sampling technique is being used?

Accepted Answer

Cluster sampling

Question 8

A survey is conducted by interviewing people at a shopping mall on a Saturday afternoon. What is the most likely source of bias in this sampling method?

Accepted Answer

Bias due to convenience sampling

Question 9

Which of the following best describes the placebo effect?

Accepted Answer

When a subject reacts favorably to a fake treatment, believing it is real

Question 10

A researcher wants to ensure that her sample of 200 students includes the same proportion of freshmen, sophomores, juniors, and seniors as in the entire university. Which sampling method should she use?

Accepted Answer

Stratified sampling

Question 11

A simulation is most appropriate for data collection when:

Accepted Answer

The situation is impractical or dangerous to reproduce in real life

Question 12

A company wants to test a new energy drink. They divide 300 participants into three age groups (18–29, 30–49, 50+), then randomly assign half of each group to receive the drink and half to receive a placebo. What experimental design is being used?

Accepted Answer

Randomized block design

Question 13

Which of the following statements about random sampling is TRUE?

Accepted Answer

Every possible sample of the same size has an equal chance of being selected in a simple random sample

Question 14

A study is conducted to determine the effect of a new fertilizer on plant growth. The researcher applies the fertilizer to half the plants and leaves the other half untreated. However, all the treated plants are placed on the sunny side of the greenhouse, while the untreated plants are on the shady side. What is the main flaw in this experimental design?

Accepted Answer

There is a confounding variable (sunlight exposure)

Question 15

Which of the following is an example of a biased sample?

Accepted Answer

Surveying only students in the statistics club to represent all students' opinions

Question 16

A researcher wants to estimate the average number of hours spent studying per week by college students. She divides the students into groups by major and randomly selects students from each group. What is the main advantage of this sampling method?

Accepted Answer

It ensures that all majors are represented in the sample

Question 17

Suppose a researcher wants to study the effect of a new exercise program on weight loss. She recruits 100 volunteers, assigns each a number, and uses a random number generator to assign 50 to the exercise group and 50 to the control group. What is the main purpose of randomization in this experiment?

Accepted Answer

To reduce the impact of confounding variables by creating similar groups

Question 18

Which of the following best describes replication in experimental design?

Accepted Answer

Repeating the experiment under the same or similar conditions to improve validity

Question 19

A researcher wants to study the effect of caffeine on reaction time. She pairs subjects by age and gender, then randomly assigns one in each pair to receive caffeine and the other to receive a placebo. What is the main benefit of this design?

Accepted Answer

It controls for confounding variables related to age and gender

Question 20

A national health agency wants to estimate the prevalence of a rare disease. They use a computer model to simulate the spread of the disease in a population of 1 million people. What is the main advantage of using a simulation in this context?

Accepted Answer

It allows the study of scenarios that would be impractical or unethical to create in real life

Data Collection and Experimental Design in Statistics

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