SOLUTION: Can you please assist with this question below: thanks in advance The time spent talking on the telephone is normally distributed with a mean of 15 minutes and a standard deviati

Algebra ->  Probability-and-statistics -> SOLUTION: Can you please assist with this question below: thanks in advance The time spent talking on the telephone is normally distributed with a mean of 15 minutes and a standard deviati      Log On


   

Question 1052747: Can you please assist with this question below: thanks in advance
The time spent talking on the telephone is normally distributed with a mean of 15 minutes and a standard deviation of 10 minutes. Calls in the upper 5% incur an extra charge. What is the longest time a person can talk without incurring the extra charge?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
mean of 15 minutes and a standard deviation of 10 minutes
the longest time a person can talk without incurring the extra charge?
<= 95%
invNorm(.95) = 1.645
z+=blue+%28x+-+mu%29%2Fblue%28sigma%29
0r
blue%28sigma%29%2Az+%2B+mu=blue+%28x%29
10*(1.645) + 15 = x = 31.45 (for these always round up to next whole number)
32min is the longest time a person can talk without incurring the extra charge