SOLUTION: Scores on a test are normally distributed with a mean of 63.2 and a standard deviation of 11.7. Find P81, which separates the bottom 81% from the top 19%.

Question 1109908: Scores on a test are normally distributed with a mean of 63.2 and a standard deviation of 11.7. Find P81, which separates the bottom 81% from the top 19%.
Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website!
to solve this problem using the normal distribution, the table of z-values is used
:
a probability of 81 corresponds to a z-value of 0.87
:
0.87 = (X - 63.2) / 11.7
:
X - 63.2 = 0.87 * 11.7 = 10.179
:
X = 63.2 + 10.179 = 73.379 approximately 73
:
a score of 73 divides the bottom 81% from the top 19%
:

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