Normal Probability of mean download time for the H&R Block website

The mean download time for the H&R Block website, www.hrblock.com is 2.5 seconds. Suppose that the download time is normally distributed, with a standard deviation of 0.5 second. What is the probability that a download time is:

a) Less than 1 second
b) Between 0.5 and 1.5 seconds
c) Above 0.5 seconds?
d) Above how many seconds are 99% of the download times?

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The mean download time for the H&R Block website, www.hrblock.com is 2.5 seconds. Suppose that the download time is normally distributed, with a standard deviation of 0.5 second. What is the probability that a download time is:
We will use EXCEL worksheet function NORMSDIST to calculate probabilities. Alternatively probabilities can be looked up in Normal Distribution tables

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c. P( 1.78 < z < 2.34).
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