1. How do I find measures of central tendency and dispersions?
Wednesday, November 3
Essential Questions
How do I find measures of central tendency and dispersions?

2. Find Measures of Central Tendency and Dispersion
7.3
Find Measures of Central Tendency and Dispersion
Example 1
Find measures of central tendency
Quiz Scores
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.

3. Find Measures of Central Tendency and Dispersion
7.3
Find Measures of Central Tendency and Dispersion
Checkpoint. Complete the following exercise.
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

4. Find Measures of Central Tendency and Dispersion
7.3
Find Measures of Central Tendency and Dispersion
Standard Deviation of a Data Set
The standard deviation s (read as “sigma”) of x1, x2, . . ., xn is

5. Find Measures of Central Tendency and Dispersion
7.3
Find Measures of Central Tendency and Dispersion
Example 2
Find measures of dispersion
Quiz Scores
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.

6. Find Measures of Central Tendency and Dispersion
7.3
Find Measures of Central Tendency and Dispersion
Example 3
Compare data sets
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 A: Mean:
Std. Dev.:

7. Find Measures of Central Tendency and Dispersion
7.3
Find Measures of Central Tendency and Dispersion
Example 3
Compare data sets
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 ____.

8. Find Measures of Central Tendency and Dispersion
7.3
Find Measures of Central Tendency and Dispersion
Checkpoint. Complete the following exercise.
Find the range and standard deviation of the data set in Exercise 1.
69, 62, 64, 67, 62, 64, 63, 65, 60, 64
Range:
69 – 60
= 9

9. Find Measures of Central Tendency and Dispersion
7.3
Find Measures of Central Tendency and Dispersion
Checkpoint. Complete the following exercise.
Compare the means and standard deviations of Set A and Set B.
Set A
Set B
Set A has a greater mean and standard deviation than Set B.

10. Find Measures of Central Tendency and Dispersion
7.3
Find Measures of Central Tendency and Dispersion
Pg. 272, 7.3 #1-13