SECTION 2.1 Frequency Distributions and Their Graphs 45 TRY IT YOURSELF 3 Use the frequency distribution from Try It Yourself 2 to construct a frequency histogram that represents the points scored by the 55 winning teams listed on page 39. Describe any patterns. Answer: Page A35 Another way to graph a frequency distribution is to use a frequency polygon. A frequency polygon is a line graph that emphasizes the continuous change in frequencies. Constructing a Frequency Polygon Draw a frequency polygon for the frequency distribution in Example 2. Describe any patterns. SOLUTION To construct the frequency polygon, use the same horizontal and vertical scales that were used in the histogram labeled with class midpoints in Example 3. Then plot points that represent the midpoint and frequency of each class and connect the points in order from left to right with line segments. Because the graph should begin and end on the horizontal axis, extend the left side to one class width before the first class midpoint and extend the right side to one class width after the last class midpoint. Frequency (number of adults) 1 3 2 4 5 6 7 136.5 172.5 208.5 244.5 280.5 316.5 352.5 388.5 Times (in minutes) Cell Phone Screen Times 424.5 You can check your answer using technology, as shown below. TI-84 PLUS Interpretation You can see that the frequency of adults increases up to a time of 316.5 minutes and then the frequency decreases. TRY IT YOURSELF 4 Use the frequency distribution from Try It Yourself 2 to construct a frequency polygon that represents the points scored by the 55 winning teams listed on page 39. Describe any patterns. Answer: Page A36 EXAMPLE 4 For help with the xy-plane and point plotting, see Integrated Review at MyLab Statistics
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