Posted by **Lyndon** on Monday, July 26, 2010 at 7:02pm.

For a normal distribution with a mean of m = 80 and a standard deviation of s = 20, find the proportion of the population corresponding to each of the following scores.

a. Scores greater than 85

b. Scores less than 100

c. Scores between 70 and 90

I believe this is the correct formula to start with but am unclear on how to finish it. Any help would be appreciated.

a. z = X-m= 85–80 = 5 = 0.25

s 20 20

b. z = X-m= 100–80 = 20 = 1.00

s 20 20

c. z = X-m= 70–80 = -10 = -0.25

s 20 20

z = X-m= 90–80 = 10 = 0.50

s 20 20

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