Download Variance • the mean of the squares of the deviations from the mean

Variance
• the mean of the squares of the
deviations from the mean for a set of data
not as bad as it looks
Variance
Standard Deviation
• the typical distance of a particular value from the mean
NOTE: the greater the standard deviation and the greater the variance, the greater the distance of the values from the mean
Standard Deviation =
1
Example 1
Variance
Calculate the variance and standard deviation
for the following data set.
48
62
81
data value ­ mean
75
77
68
square of the difference
48
62
81
75
77
68
Total
Variance = Standard Deviation = 2
Example 2
Jarrod scored 5 goals in 1 game, 2 goals in each of 4 games, 1 goal in each of 4 games and no goals in 1 game. Henry his team mate scored 3 goals in each of 2 games, 2 goals in each of 3 games, and 1 goal in each of 5 games.
BASED on these games which player is more consistent goal scorer?
1st Determine the mean
Jarrod
Henry
Total # of goals
Total # of games
Mean
3
Determine the Range
Determine the Standard Deviation
Data value
Data value ­ mean
Square of Differences
5
2
2
2
2
1
1
1
1 0
4
Determine the Standard Deviation
Data value
Data value ­ mean
Square of Differences
3
3
2
2
2
1
1
1
1 1
5
Homework
page 146 # 5, 7
6