The following frequency distribution reports the electricity cost for a sample o

Question

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.

Explanation / Answer

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

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