Essential Questions

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Wednesday, November 3
Essential Questions

• How do I find measures of central tendency and
  dispersions?

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Find measures of central tendency
Example 1
Find the mean, median, and mode of the data set.
19, 15, 22, 17, 21, 17, 25, 18, 17
Solution
To find the mean, divide the sum of the scores by
the number of scores.
To find the median, first order the quiz scores
from least to greatest.
15, 17, 17, 17, 18, 19, 21, 22, 25
Because there is an odd number of scores, the
median is the middle number, _____.
There is one mode, _____, because this number
occurs most frequently.
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Checkpoint. Complete the following exercise.

1. The data set below gives the recorded speeds (in
   mi/h) of 10 different cars on a local highway
   during a week day.

69, 62, 64, 67, 62, 64, 63, 65, 60, 64
Find the mean, median and mode of the data set.
60, 62, 62, 63, 64, 64, 64, 65, 67, 69
Median 64
Mode 64
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Standard Deviation of a Data Set
The standard deviation s (read as sigma) of x1,
x2, . . ., xn is
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Find measures of dispersion
Example 2
Find the range and standard deviation for the
quiz scores in Example 1.
19, 15, 22, 17, 21, 17, 25, 18, 17
Solution
To find the range, subtract the least data value
from the greatest data value.
To find the standard deviation, substitute the
scores and the mean into the formula.
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Compare data sets
Example 3
The lists show the number of memberships sold
each month for one year by two competing athletic
clubs. Compare the mean and standard deviation
for the numbers of memberships sold by the two
athletic clubs.
Club A 12, 9, 14, 6, 10, 11, 19, 6, 17, 11, 4, 13
Club B 17, 10, 22, 15, 14, 19, 4, 8, 12, 22, 20,
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Solution
Club A Mean
Std. Dev.
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Compare data sets
Example 3
The lists show the number of memberships sold
each month for one year by two competing athletic
clubs. Compare the mean and standard deviation
for the numbers of memberships sold by the two
athletic clubs.
Club A 12, 9, 14, 6, 10, 11, 19, 6, 17, 11, 4, 13
Club B 17, 10, 22, 15, 14, 19, 4, 8, 12, 22, 20,
5
Solution
Club B Mean
Std. Dev.
Athletic Club ___ has a greater mean and a
greater standard deviation than Athletic Club
____.
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Checkpoint. Complete the following exercise.

1. Find the range and standard deviation of the data
   set in Exercise 1.

69, 62, 64, 67, 62, 64, 63, 65, 60, 64
69 60
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Range
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Checkpoint. Complete the following exercise.

1. Compare the means and standard deviations of Set
   A and Set B.

Set A
Set B
4 7 5 9 10
2 6 5 4 3
Set A has a greater mean and standard deviation
than Set B.
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Pg. 272, 7.3 1-13