SOLUTION: A fire department in a rural county reports that its response time to fires is approximately Normally distributed with a mean of 22 minutes and a standard deviation of 11.9 minute

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Question 667206: A fire department in a rural county reports that its response time to fires is approximately
Normally distributed with a mean of 22 minutes and a standard deviation of 11.9 minutes.
Approximately what proportion of their response times is over 30 minutes?
a)0.03
b)0.21
c)0.25
d)0.75
e)0.79
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,Re TY

You did not say how You determine the P-value given the z-value

NORMSDIST(.6723) is one such way of doing that ...using an Excel function NORMSDIST.

Chart or TI calculator works as well.

μ = 22  ,  σ =11.9  and z = (30-22)/11.9

P(x>30) = 1 -P(z ≤ .6723) = 1- NORMSDIST(.6723)= 1-.75 = .25