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Frequency Distribution Charts

The following frequency distribution reports electricity cost for a sample of 50 two-bedroom apartments in Albuquerque, New Mexico during 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. Estimate the mean cost.
B. Estimate the standard deviation
C. Use the Empirical Rule to estimate the proportion of costs within two standard deviations of the mean. What are these limits?

Solution Preview

Solution:
A. Estimate the mean cost.

Electiricty cost (x) frequency(f) d d*f
80 to 100 3 90 270
100to 120 8 110 880
120 to 140 12 130 1560
140 to 160 16 150 2400
160 to 180 7 170 1190
180 to 200 4 190 760

total 50 ...

Solution Summary

The solution shows how the mean cost and (estimate) standard deviation is calculated by providing steps to determining solution.

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