What conditions indicate that we should use relative frequency distributions rather than frequency distributions?
 Use frequency distributions if we focus on comparing different classes
 Use relative frequency distributions if we focus on comparing different classes to the whole
What is the difference between a frequency bar graph and a relative-frequency bar graph?
Bar graphs give a visual comparison of two or more data sets.
Frequency bar graphs focus the attention on the frequency of the occurrences of the categories.
Frequency bar graphs are useful when we want to compare the different parts, not the parts to the whole sample
(population).
Relative frequency bar graphs are useful when we want to compare different parts to the whole sample (population)
Explain the difference between a frequency histogram and a relative-frequency histogram.
 When do we use a frequency histogram?


A frequency histogram displays the frequencies (counts) of the classes.
When we want to compare the different classes, not the classes to the entire data set.
 When do we use a relative-frequency histogram?
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A relative-frequency histogram displays the relative frequencies (or percentages)
When we want to compare the different classes, and the classes to the entire data set.
List two differences between a histogram and a bar graph.
Histogram:
Displays continuous data
Rectangles must touch
Displays one data set
Bar graph:
Displays categorical data
Displays numerical data (sometimes)
Rectangles do not touch.
Compares two or more data sets
Are there any differences between a box plot and a histogram?
Box plots:
 Show numerical summary
 Compare two or more samples at the same time (in one graph)
Histograms:
 Show data of one sample graphically
 Do not show numerical summary
 Do not apply to small data sets (20 or less data points)
Are there any similarities between a box plot and a histogram?
 They both show continuous (numerical) data
 They both handle large data sets
 They both show outliers (if any)
Under what condition is the median a better measure of the center of a data set than is the mean?
 Use the median if outliers are present.
 Use the mean if no outliers are present.
© Stanley Leung, WOU