Q: Which of the following is a correct formula for finding the class midpoint?

$$\text{Class midpoint} = \frac{\text{Lower class limit} + \text{Upper class limit}}{2}$$

Question 1

Given the frequency distribution for daily commute times in Los Angeles, what is the relative frequency for the class 30–44 minutes? Use the formula $$	ext{Relative frequency} = \frac{	ext{Class frequency}}{	ext{Sum of all frequencies}}.$$

Accepted Answer

$$\frac{14}{50} = 0.28$$

Question 2

What is the class width for the frequency distribution with classes 0–14, 15–29, 30–44, etc.?

Accepted Answer

$$15$$

Question 3

Which of the following best describes the shape of the histogram for the Los Angeles commute times?

Accepted Answer

Skewed to the right (positively skewed)

Question 4

If you want to compare the distribution of commute times between Los Angeles and Boise, which type of graph would be most effective?

Accepted Answer

Relative frequency polygon

Question 5

What is the cumulative frequency for commute times less than 60 minutes in Los Angeles?

Accepted Answer

$$43$$

Question 6

Which of the following is NOT a feature of a histogram?

Accepted Answer

Bars are separated by gaps to show class boundaries

Question 7

A misleading graph uses a vertical axis that starts at a value greater than zero. What is the main effect of this design?

Accepted Answer

It exaggerates differences between groups

Question 8

Which of the following is a correct formula for finding the class midpoint?

Accepted Answer

$$	ext{Class midpoint} = \frac{	ext{Lower class limit} + 	ext{Upper class limit}}{2}$$

Question 9

Which type of graph is best for displaying the cumulative frequency of a data set?

Accepted Answer

Ogive

Question 10

A frequency distribution has a large gap between two groups of values. What might this indicate?

Accepted Answer

The data may come from two different populations

Question 11

Which of the following is a feature of a stemplot (stem-and-leaf plot) that distinguishes it from a histogram?

Accepted Answer

It retains the original data values

Question 12

If a distribution is described as 'skewed to the left,' what does this mean?

Accepted Answer

The left tail is longer than the right tail

Question 13

Which of the following graphs is most appropriate for displaying the distribution of a categorical variable such as 'type of rehabilitation required by patients'?

Accepted Answer

Bar graph

Question 14

A pie chart is used to display which type of data?

Accepted Answer

Qualitative (categorical) data

Question 15

Which of the following is a potential problem with pictographs?

Accepted Answer

They can exaggerate differences by using area or volume instead of length

Question 16

Which of the following best describes a scatterplot?

Accepted Answer

A plot of paired $$(x, y)$$ quantitative data

Question 17

If the frequencies in a histogram increase to a maximum and then decrease symmetrically, what is the likely shape of the distribution?

Accepted Answer

Bell-shaped (normal distribution)

Question 18

Which of the following is the correct formula for calculating class width?

Accepted Answer

$$	ext{Class width} = \frac{	ext{Maximum value} - 	ext{Minimum value}}{	ext{Number of classes}}$$

Question 19

Which of the following is a reason for constructing a frequency distribution?

Accepted Answer

To summarize large data sets and gain insight into the nature of the data

Question 20

Which of the following statements about outliers is correct?

Accepted Answer

Outliers are sample values that lie very far away from the vast majority of other sample values

Exploring Data with Tables and Graphs: Frequency Distributions, Histograms, and Graphical Summaries

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