SOLUTION: Please help me understand this question for my exam tomorrow. Find the z-score such that the interval within z standrard deviations of the mean for a normal distribution contains

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Question 324820: Please help me understand this question for my exam tomorrow. Find the z-score such that the interval within z standrard deviations of the mean for a normal distribution contains (A)50% of the probability and (B)90% of the probability.
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
the probabilities are symmetric about the mean (which has a z-score of 0)

for 50% , go into the z-score table and find the .25 area (probability)
___ the associated z-score is above AND below the mean , giving a 50% interval

this may be helpful ___ http://www.mathsisfun.com/data/standard-normal-distribution-table.html