Normal distribution call centre wait times above 30 seconds

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xargon
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Hi,

This is not a physics question. However, I was hoping someone could help me.

A call centre sets a quality target of answering the telephone within 30 seconds. The results of monitoring show a normal distribution with an average answer time of 28 seconds and a standard deviation of 2 seconds.
question: what percentage of customers are still being kept waiting too long?

Thanks,

xargon
 

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1 SD to the right of the mean is 30 s. I think you need to work out P(Z < 30) and take that away from 1, though I can't remember how to do that.
 
about 68% of the area of the normal distribution lies between minus 1 sd and plus sd from the mean. So I think you can find the answer from there by yourself...