The following frequency distribution reports electricity cost for sample of 50 two-bedroom apartments in Albuquerque, New Mexico throughout the month of May last year.
|
Electricity Cost
|
Frequency
|
|
$ 80 up to $100
|
3
|
|
100 up to 120
|
8
|
|
120 up to 140
|
12
|
|
140 up to 160
|
16
|
|
160 up to 180
|
7
|
|
180 up to 200
|
4
|
|
Total
|
50
|
a) Determine the mean cost.
b) Determine the standard deviation.
c) Use the Empirical Rule to estimate the proportion of costs in two standard deviations of mean. What are these limits?