Question 1

Which of the following best describes a variable in a statistical study?

Accepted Answer

A value that is intentionally manipulated or measured in an experiment.

Question 2

In a study where Ellie wants to know if plants will grow faster if they listen to Taylor Swift music, what is the dependent variable?

Accepted Answer

The height of each plant after the course of a month.

Question 3

Given the exam scores: 82, 72, 88, 90, 100, 92, 80, 75, 87, 88, what is the median score?

Accepted Answer

Median = $$\frac{87 + 88}{2} = 87.5$$

Question 4

Which measure of central tendency is most appropriate to report for a salary distribution that is skewed right with outliers?

Accepted Answer

Median, because it is resistant to outliers.

Question 5

A graph showing percentages of respondents supporting background checks for gun buyers is misleading if:

Accepted Answer

The vertical scale does not begin at zero.

Question 6

What should be fixed in a misleading bar graph to make it accurate?

Accepted Answer

The vertical scale should begin at zero.

Question 7

Jimmy wants to know how all Americans feel about debt-relief programs for people with student loans. He surveys people in the student lounge on campus. Is this an appropriate sample?

Accepted Answer

No, because it is not representative of all Americans.

Question 8

Scientists want to determine the effect of smoking tobacco around newborns. Should they use a designed experiment or an observational study?

Accepted Answer

Observational study, because a designed experiment would be unethical.

Question 9

If Professor Jones’s class has a mean score of $$80$$ and a standard deviation of $$5$$, what is the z-score for a student who scored $$94$$?

Accepted Answer

$$z = \frac{94 - 80}{5} = 2.8$$

Question 10

In a scatterplot showing the percentage of population using the internet and their life expectancy, which of the following best describes a negative association?

Accepted Answer

As internet usage increases, life expectancy decreases.

Question 11

Given the regression equation $$y = b_0$ + b_1$ x$$, if $$b_1 = 0.1337$ and b_0$ = 12.471$$, what does $$b_1$$ represent?

Accepted Answer

For each one inch increase in height, head circumference increases by $$0.1337$$ inches.

Question 12

If the regression equation for predicting head circumference from height is $$y = 12.471 + 0.1337x$$, what is the predicted head circumference for a child who is $$25$$ inches tall?

Accepted Answer

$$y = 12.471 + 0.1337 	imes 25 = 15.8135$$ inches

Question 13

Which of the following is NOT a reason to use the median instead of the mean for skewed data?

Accepted Answer

Median is always the most frequent value.

Question 14

If a data set has a range of $$28$$ and an interquartile range (IQR) of $$10$$, what does this suggest about the spread of the data?

Accepted Answer

Most of the data is concentrated within the middle $$50\% of $$values.

Question 15

Which of the following best describes an observational study?

Accepted Answer

A study where the researcher observes subjects without manipulating variables.

Question 16

If a boxplot shows a data set with a long right whisker, what is the shape of the distribution?

Accepted Answer

Skewed right

Question 17

Which of the following is a plausible reason for an outlier in a salary distribution of recent college graduates?

Accepted Answer

A graduate who started a high-paying job in a specialized field.

Question 18

If the correlation coefficient $$r$$ between height and head circumference is $$0.91$$, what does this indicate?

Accepted Answer

There is a strong positive linear relationship between height and head circumference.

Step-by-Step Study Guide for Descriptive Statistics Exam

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