Q: Given the following counts from a survey: 18 people prefer the game, 12 prefer commercials, 9 won’t watch, and 1 gave no answer. What is the percentage of people who prefer the game?

$$ \frac{18}{40} \times 100 = 45\% $$

Question 1

Which of the following best describes the area principle in data visualization?

Accepted Answer

The area occupied by a part of the graph should correspond to the magnitude of the value it represents.

Question 2

A frequency table for a categorical variable should include which of the following?

Accepted Answer

Counts and/or percentages for each category.

Question 3

Which type of chart is most appropriate for displaying the distribution of a single categorical variable?

Accepted Answer

Bar chart

Question 4

Suppose you have a contingency table showing survival (Alive/Dead) and ticket class (First/Second/Third/Crew) for Titanic passengers. What does the marginal distribution of survival show?

Accepted Answer

The total counts or percentages of passengers who survived or died, regardless of ticket class.

Question 5

In a contingency table, what does it mean if the conditional distributions of one variable are the same for every category of the other variable?

Accepted Answer

The variables are independent.

Question 6

Which of the following is a potential pitfall when interpreting pie charts?

Accepted Answer

The percentages may add up to more than 100% if categories overlap.

Question 7

A segmented bar chart is used to:

Accepted Answer

Show the conditional distribution of one categorical variable within each category of another variable.

Question 8

Simpson’s Paradox occurs when:

Accepted Answer

Combining percentages across different groups leads to misleading conclusions.

Question 9

Given the following counts from a survey: 18 people prefer the game, 12 prefer commercials, 9 won’t watch, and 1 gave no answer. What is the percentage of people who prefer the game?

Accepted Answer

$$ \frac{18}{40} 	imes 100 = 45\% $$

Question 10

Which of the following best describes a conditional distribution?

Accepted Answer

The distribution of one variable for just those cases that satisfy a specified condition on another variable.

Question 11

A company wants to compare the effectiveness of two sales representatives across two products. Peter closes 90% of printer paper sales and 50% of USB flash drive sales. Katrina closes 95% of printer paper sales and 75% of USB flash drive sales. However, Peter’s overall closing rate is higher. What statistical phenomenon does this illustrate?

Accepted Answer

Simpson’s Paradox

Question 12

Which of the following is NOT a requirement for making a bar chart or pie chart of categorical data?

Accepted Answer

The data must be numerical and continuous.

Question 13

If you want to compare the proportion of social networking users across five countries, which display would be most appropriate?

Accepted Answer

A segmented bar chart or mosaic plot

Question 14

In a contingency table, what does a cell represent?

Accepted Answer

The count for a combination of values of the two variables.

Question 15

Why is it important not to combine percentages across very different groups?

Accepted Answer

It can lead to misleading conclusions due to Simpson’s Paradox.

Question 16

Which of the following is a correct interpretation of a mosaic plot?

Accepted Answer

The width of each bar is proportional to the size of the group, and the height shows the conditional distribution.

Question 17

A bar chart shows the number of website visits by source: Google, Direct, E-mail, Bing, Yahoo, Facebook, Mobile, and Other. If Google has 130,158 visits out of a total of 226,925, what is the relative frequency for Google?

Accepted Answer

$$ \frac{130,158}{226,925} 	imes 100 = 57.36\% $$

Question 18

Which of the following is a key reason to use a picture (graph) to display categorical data?

Accepted Answer

Pictures reveal patterns and features that may not be obvious in tables of numbers.

Question 19

If a segmented bar chart shows that the proportion of survivors is much higher in first class than in third class on the Titanic, what can you conclude?

Accepted Answer

Survival is associated with ticket class.

Displaying and Describing Categorical Data: Chapter 2 Study Notes

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