Page 422 - Algebra 1

Stem-and-leaf plots are used to show the distribution of data. In the stem-and-leaf plot for Example 1, there is an unequal distribution of temperatures in the 80’s. This may not have been as obvious when the data was in a continuous list. When organizing the data by place values, it becomes easier to identify unequal distributions.
Stem-and-leaf plots are used to find measures of central tendency and other statistical measures because the actual data points are included in the plot. One of the many statistical measures that are helpful is relative frequency.
In an experiment, the number of times an event happens divided by the total number of trials is the relative frequency of that event.
Analyzing a Stem-and-Leaf Plot
Use the stem-and-leaf plot from Example 1 to find the following statistical measures.
a. median
SOLUTION
To find the median, find the middle value(s). For these data there are
two middle values. The 15th and 16th values are 78 and 80. Find the average of 78 and 80.
22
The median of the data is 79˚F.
b. mode
SOLUTION
The mode is the value or values that occur most frequently. There are 4 values that occur 3 times: 78, 80, 81, and 83. These are the modes.
c. range
SOLUTION
The range is the difference between the greatest and least value in the set. The greatest data value is 87; the least data value is 53. The range is 34˚F.
d. relative frequency of 80
SOLUTION
The data value 80 occurs 3 times. There are a total of 30 data values.
_3 =_1 =0.10=10% 30 10
Example
2
Caution
The data must be in order before finding the middle value(s).
78+80 = 158 =79 __
Hint
Relative frequency
can be expressed as a fraction, a decimal, or a percent.
OnlineConnection www.SaxonMathResources.com
Lesson 62 407