Ali K. answered • 06/03/21
Tutor
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(573)
UT Austin PhD in Electrical + Computer Engineering | Algorithms Expert
Yes, you can use the standard Normal table to find this probability as follows:
Looking at the table, the CDF at 2.55 reaches 0.9946, meaning that the probability that standard normal distribution is more than 2.55 is almost 0.0054.
Similarly, the probability of being less than -2.55 is 0.0054.
Therefore, the probability of standard Normal being in the middle region is 1-2*0.0054 = 0.9892.
Ali K.
tutor
You probably looked up 2.72 in the table instead of 0.272.
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06/07/21
Brian P.
That seemed to make perfect sense, until I tried this problem. mean=51 SD=22 (Prob. between 45 57) 45-51 -------= -.2727 Z chart=.9967 22 1-.9967=.0033 1-2(.0033)= .9934 Yet the answer I am told is= .215 What is different about this problem than the example you calculated?06/07/21