I am having trouble with the below question"
The time spent waiting for a prescription to be prepared at a chemist's shop is normally distributed with mean 15 minutes and standard deviation 2.8 minutes. Find the probability that the waiting time is:
a) more then $20$ minutes.
So is what I am doing correct?
t ~ N(15,7.84)
P(t > 20)
P(Z> 20-15 / 2.8)
= 0.03707
Is this correct?
Thanks!