and a standard deviation of $16?a) what is the probability that a randomly selected bill will be less than $80 per month?

a) Z = 80-120 / 16 = -2.5 standard deviations from the mean

look up on Z chart to find probability: P = .0062 or 0.062%

b) Z = 140-120 / 16 = 1.25 standard deviations from the mean

on Z chart, the probability = 0.8944, but that is the probability for LESS THAN $140

for GREATER THAN we need to subtract it from 1: 1 -0.8944 = 0.1056 or 10.56%

c) for between $100 and $140 we have to subtract the probability of each

P(Z at $140) = 0.8944

P(Z at $100) = 0.1056

The difference is 0.7888 or 78.88%

Secure Information

Content will be erased after question is completed.

Enter the email address associated with your account, and we will email you a link to reset your password.

Forgot your password?

Sign Up