3. Internet service providers (ISP) need to resolve customer problems as quickly

Question

3. Internet service providers (ISP) need to resolve customer problems as quickly as possible. For one ISP, past data indicate that the likelihood is .70 that customer calls regarding Internet service interruptions are resolved within one hour. Out of the next 8 customer calls about interrupted service,

A. What is the probability model for this case? ____________________________

B. What is the probability that exactly 7 will be resolved within one hour?

C. What is the probability that all eight will be resolved within one hour?

D. How many customers would be expected to have their service problems resolved within one hours?

Explanation / Answer

A) This is binomial distribution.

p = 0.7

n = 8

P(X = x) = 8Cx * 0.7x * (1-0.7)8-x

B) P(X = 7) = 8C7 * 0.77 * 0.31 = 0.1977

C) P(X = 8) = 8C8 * 0.78 * 0.30 = 0.0576

D) expected number = n * p = 8 * 0.7 = 5.6

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