In: Statistics and Probability
A phone call to the service center has a normal distribution with mean 10 min and standard deviation 2 min. During one day there were 5 phone calls and during the other day there were 6 calls. What is the probability that the sample average taken on each of the two days is at most 11?
Solution :
Given that ,
mean =
= 10
standard deviation =
= 2
n = 6
= 10
=
/
n = 2 /
6
P(
> 11) = 1 - P(
< )
= 1 - P[(
-
) /
< (11 - 10) / 2 /
6 ]
= 1 - P(z < 1.22)
= 1 - 0.8888
= 0.1112