Question 1

Which of the following best describes the main reason why statisticians use samples instead of studying entire populations?

Accepted Answer

Because it is usually impractical or impossible to collect data on the entire population.

Question 2

A researcher wants to estimate the average cholesterol level of adults in a city. She collects data from 200 randomly selected adults. What is the population in this context?

Accepted Answer

All adults in the city.

Question 3

Which of the following is an example of sampling bias?

Accepted Answer

Surveying only people who respond to an online poll about internet usage.

Question 4

In the 1936 Literary Digest poll, why was the sample biased?

Accepted Answer

Because only high-income earners with phones were included, underrepresenting low-income voters.

Question 5

Which of the following statements about randomization in sampling is TRUE?

Accepted Answer

Randomization helps protect against both known and unknown sources of bias.

Question 6

Suppose you want to estimate the average height of all students at your university. Which sampling method is most likely to produce a representative sample?

Accepted Answer

Randomly selecting students from the entire student directory.

Question 7

Which of the following best explains why increasing the sample size reduces variability?

Accepted Answer

Larger samples tend to average out the natural differences between individuals, leading to more stable estimates.

Question 8

A pollster wants to estimate the proportion of voters who support a new policy. She randomly selects 500 voters from a city of 1 million. According to statistical principles, what is the most important factor in determining the accuracy of her estimate?

Accepted Answer

The size of the sample ($$n).$$

Question 9

Which of the following is a key disadvantage of conducting a census instead of a sample?

Accepted Answer

A census is often impractical, expensive, and time-consuming.

Question 10

A soup company wants to ensure the taste of their soup is consistent. They take a spoonful from a large pot to test. What statistical concept does this illustrate?

Accepted Answer

Using a sample to make inferences about a population.

Question 11

Which of the following best describes the difference between bias and variability in sampling?

Accepted Answer

Bias is a systematic favoring of certain outcomes, while variability is the natural fluctuation from sample to sample.

Question 12

A researcher wants to match her sample to the population on every possible characteristic (age, income, education, etc.). Why is this approach not practical?

Accepted Answer

Because it is impossible to know all characteristics that might be important.

Question 13

Suppose a pollster only surveys people who answer their landline phones. Which group is most likely to be underrepresented in the sample?

Accepted Answer

People who use cell phones exclusively.

Question 14

If a sample is biased, which of the following is TRUE?

Accepted Answer

There is usually no way to fix the bias after the sample is drawn.

Question 15

A university wants to estimate the average GPA of its students. Which of the following sampling methods is most likely to introduce bias?

Accepted Answer

Surveying only students who visit the library.

Question 16

Which formula represents the sample size in statistics?

Accepted Answer

$$n$$

Question 17

A pollster uses a random number generator to select phone numbers for a survey. What is the main advantage of this approach?

Accepted Answer

It helps protect against both known and unknown sources of bias.

Question 18

Which of the following statements about sample size and population size is correct?

Accepted Answer

The accuracy of a sample depends primarily on the sample size, not the population size.

Question 19

A medical researcher wants to estimate the prevalence of a rare disease. She samples 1,000 people from a city of 2 million. What is the main statistical reason this sample can still provide a reliable estimate?

Accepted Answer

Because the reliability of the estimate depends on the sample size, not the population size.

Question 20

Which of the following is NOT a reason why a census is often impractical?

Accepted Answer

A census always produces biased results.

Chapter 10: Sample Surveys – The Three Big Ideas of Sampling

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