Question 1122077: A study on the delivery time of mail between two locations has found that the data follows a normal distribution. The study has also found that on average, mail takes up to five days to arrive with a standard deviation of 0.75 days. Using this information, what is the probability that the mail will take at most 4 days to arrive?
A) 0.0918
B) 0.9082
C) 0.50
D) 0.4082
E) 1.00
Answer by jim_thompson5910(35256)   (Show Source):
You can put this solution on YOUR website! Use a table or a calculator such as this one provided at the link below
http://onlinestatbook.com/2/calculators/normal_dist.html
I prefer a calculator option because it's faster, more efficient, less error prone, etc. If you use the calculator at the link, then type in 5 for the mean, 0.75 for the SD (Standard Deviation) and click the "below" button. In the box next to "below", type in 4. All of this will compute 
Using the calculator, we see that the answer is 0.0912 which is fairly close to 0.0918; chances are that your teacher is having you use a Z table, which might explain the slight discrepancy
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