Question

4-100 Phoenix water is provided to approximately 1.4 million people who are served through more than 362,000. All accounts are metered and billed monthly. The probability that an acoount has an error in a month is 0.001, and accounts can be assumed to be independent. (a) What are the mean and standard deviation of the number of account errors each month? (b) Approximate the probability of fewer than 340 errors in a month (c) Approximate a value so that the probability that the number of errors exceeds this value is 0.1 (d) Approximate the probability of more than 425 errors per month in the next three months. Assume that results between moths are independent.

Answer 1

Solution Given dala oe ha t aleulati man an Alandend devialion sample &죵 probability lhat account h0.1 an emBY Mean ese V -362x10 1 x10 -3+3 362メ。 362灯 H eolda landa daon 3 61,638 19.0168 LbHerg, oe towe o alcula^ P(x4340)- 340-o.S3 339,3- 362\ . . .0 168 l9. DI G8

usin - 1.28 24.3IS 362 3S6·3415 386 son 386 NOTE THANE uo