Measures of Center Tendency and Dispersion

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MEASURES OF CENTER TENDENCY
AND DISPERSION
Kayla Gonzalez
Miranda Arce
Gabriela Loriga
Oscar Bardinas
Emmanuel Cortes
MEASURES OF CENTRAL TENDENCY AND OUTLIERS
o One way to summarize a set of data is to use a measure of central tendency. Mean,
median, and mode are all measures of central tendency.
o The measure of central tendency that best describes a data set may depend on
whether the data set has an outlier.
o An outlier is a data value that is much greater or less than the other values in the
set.
MEAN, MEDIAN, AND MODE
o The mean equals sum of the data values
total number of data values
oUse mean to describe the middle of a set of data that does not have an outlier.
o The median is the middle value in a data set when the values are arranged in
order. For a set containing an even number of data values, the median is the mean of
the two middle data values.
o Use median to describe the middle of a set of data that does have an outlier.
o The mode is the data item that occurs the most amount of times. A data set can have
no mode, one mode, or more than one mode.
o Use mode when the data are nonnumeric or when choosing the most popular item.
MEAN, MEDIAN, AND MODE
Practice Problem 1
What are the mean median and mode of the bowling score below? Which measure
of central tendency best describes the scores?
Bowler
1
2
3
4
5
6
7
8
Score
104
117
104
136
189
109
113
104
Mean:
Median:
Mode:
MEAN, MEDIAN, AND MODE
Practice Problem 2
Your grades on three exams are 80, 93, and 91. What grade do you need on the
next exam to have an average of 90 on the four exams?
MEASURE OF DISPERSION AND RANGE OF A SET
OF DATA
o A measure of dispersion describes how dispersed, or spread out, the values in a
data set are.
o One measure of dispersion is range.
o The range of a set of data is the difference between the greatest and least data
values.
MEASURE OF DISPERSION AND RANGE OF A SET
OF DATA
Practice Problem 3
Number of Weekly Sales
The pie chart on the right shows the numbers of weekly sales a
salesperson made in the first nine weeks of a ten-week sales
period. The salesperson’s target is an average of 14 sales each
week. How many sales does the sales person need in the tenth
week to meet the target average?
12(1)
14(3)
13(2)
15(3)
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