Question 1

Which of the following best describes a confounding variable in an observational study?

Accepted Answer

A variable that is not considered in the study but affects the value of the response variable, making it difficult to determine the actual relationship between explanatory and response variables.

Question 2

A researcher wants to compare the average cholesterol levels between two groups of patients: those who exercise regularly and those who do not. Which study design is most appropriate?

Accepted Answer

Cross-sectional study

Question 3

Which of the following sampling methods does NOT require a sampling frame?

Accepted Answer

Cluster sampling

Question 4

Suppose a sample of 100 students is selected from a university population using simple random sampling. What is the probability that any one student is selected?

Accepted Answer

$$ \frac{1}{N} $$ where $$N is $$the population size

Question 5

Which of the following is a parameter?

Accepted Answer

The mean cholesterol level of all adults in the United States.

Question 6

A frequency distribution must satisfy which of the following conditions?

Accepted Answer

The sum of all relative frequencies must add up to 1.

Question 7

Which measure of central tendency is most resistant to extreme values (outliers)?

Accepted Answer

Median

Question 8

Given a data set with $$Q_1 = 25$, Q_3$ = 65$$, what is the interquartile range (IQR)?

Accepted Answer

$$ 40 $$

Question 9

In which situation is the interquartile range (IQR) preferred over the standard deviation as a measure of dispersion?

Accepted Answer

When the data are skewed or have outliers.

Question 10

A sample of 10 exam scores has a mean of 75 and a standard deviation of 8. What is the $$z-$$score for a student who scored 90?

Accepted Answer

$$ z = \frac{90 - 75}{8} = 1.875 $$

Question 11

Which of the following best describes an observational study?

Accepted Answer

A study in which the researcher observes individuals and measures variables of interest without influencing the responses.

Question 12

Which of the following is an example of underrepresentation in sampling?

Accepted Answer

A sample contains a lower proportion of minority students than the population.

Question 13

Which of the following is true about the standard deviation?

Accepted Answer

It measures the spread of the data around the mean.

Question 14

If a distribution is positively skewed, which of the following is most likely true?

Accepted Answer

Mode \u003c Median \u003c Mean

Question 15

Which of the following best describes a statistic?

Accepted Answer

A numerical summary of a sample.

Question 16

A researcher divides a population into groups based on age and then randomly selects individuals from each group. Which sampling method is being used?

Accepted Answer

Stratified sampling

Question 17

Which of the following is a disadvantage of using convenience sampling?

Accepted Answer

It may not be representative of the population.

Question 18

Which formula is used to calculate the $$z-$$score for a value $$x in a $$population with mean $$\mu$$ and standard deviation $$\sigma$$?

Accepted Answer

$$ z = \frac{x - \mu}{\sigma} $$

Question 19

Which of the following best describes marginal distribution in a two-way table?

Accepted Answer

The distribution of one variable among all individuals, ignoring the other variable.

Foundations of Statistics: Data Collection, Summarizing, and Descriptive Measures

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