Question
(BACKGROUND ONLY) The manager of a computer help desk operation has collected enough data to conclude that the distribution of time per call is normally
(BACKGROUND ONLY) The manager of a computer help desk operation has collected enough data to conclude that the distribution of time per call is normally distributed with a mean equal to 8.21 minutes and a standard deviation of 2.14 minutes. Based on this, what is the probability that a call will last longer than 13 minutes?
(I UNDERSTAND THIS)
The given information is, = 8.21 minutes and = 2.14 minutes.
P (call will last more than 13 minutes) = P (X>13), where x is a normal variate.
For x=13, the z-score as follows:
z=(x- )/ .
z= (13-8.21)/2.14 = 4.79/2.14= 2.2383.
Use the z- calculator or Standard-Normal chart,
Then the probability P (X>13) =P (z>2.2383)
= 0.0125. <------- ????
QUESTION: HOW DO I USE THE STANDARD-NORMAL CHART, TO CONVERT
P (X>13) =P (z>2.2383) = 0.0125?????
Would you please explain. step by step. thank you very much.
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