# Thread: Probability Question

1. ## Probability Question

WNAE, an all-news, all-the-time station, finds that the distribution of the length of time listeners are tuned to the station is normal, with a mean of 15 minutes and a standard deviation of 3.5 minutes. What is the probability that a particular listener will tune for:

a. More than 20 minutes?
b. For 20 minutes, or less?
c. For between 10 and 12 minutes.
I know the mean and standard deviation listed above, but I do not know how to get to the probability with the answers to the following...
PLEASE HELP!!!!

2. Originally Posted by kendrick02
WNAE, an all-news, all-the-time station, finds that the distribution of the length of time listeners are tuned to the station is normal, with a mean of 15 minutes and a standard deviation of 3.5 minutes. What is the probability that a particular listener will tune for:

a. More than 20 minutes?
b. For 20 minutes, or less?
c. For between 10 and 12 minutes.
I know the mean and standard deviation listed above, but I do not know how to get to the probability with the answers to the following...
PLEASE HELP!!!!
a. X = 20 => Z = 10/7. Therefore Pr(X > 20) = Pr(Z > 10/7) = 1 - Pr(Z < 10/7) = 1 - Pr(Z < 1.4286). Get Pr(Z < 1.4286) from your tables.

b. and c. are done in a similar way. So please show what you try and where you get stuck.