Homework SourseThe following frequency distribution reports the electricity
The following frequency distribution reports the 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
Use the Empirical Rule to estimate the proportion of costs within two standard deviations of the mean. What are these limits? (Round your answers to 2 decimal places.)
| The following frequency distribution reports the electricity cost for a sample of 50 two-bedroom apartments in Albuquerque, New Mexico, during the month of May last year. |
Solution
a)
Thus,
Mean = Sum(xf) / Sum(f) = 141.2 [ANSWER]
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B)
Thus,
Variance = [Sum(x^2f) - Sum(xf)^2/Sum(f)]/[Sum(f)-1] = 688.3265306
Standard deviation = sqrt(Variance) = 26.23597779 [ANSWER]
c)
u - 2s = 88.72804442
u + 2s = 193.6719556 [ANSWERS]
| x | f | x f | x^2 f |
| 90 | 3 | 270 | 24300 |
| 110 | 8 | 880 | 96800 |
| 130 | 12 | 1560 | 202800 |
| 150 | 16 | 2400 | 360000 |
| 170 | 7 | 1190 | 202300 |
| 190 | 4 | 760 | 144400 |
