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Measures of Central Tendency
and
Measures of Dispersion
Formulas
x
x
x


n
mean of ungrouped data
(here x is the data point)
f  x 


n
mean of grouped data
(here x is the midpoint of a group)
Formulas
 x  x 
2
s
n1
standard deviation
Tom Ball, an avid jogger,
kept detailed records of
the number of miles he ran
per week during the past
six months. The frequency
distribution summarizes
his records. Find the
mean, median, and mode
of the number of miles per
week that Tom ran. Draw
a box and whiskers plot of
the data.
Miles run
per week
0
1
2
3
4
5
6
7
Number
of weeks
3
2
5
1
5
6
3
1
The weight (in pounds) of the ten Truly
Amazing Dudes are as follows:
152 196
144 139166
83 186 157140 138
Find the mean and standard deviation of
the weights.