Question

Stacy took a math test whose mean was 70 and standard deviation was 5. The total points possible was 100. Stacey's results were reported to be at the 95th percentile. What was Stacey's actual exam score, rounded to the nearest whole number?

Answer 1

Let X be the random variable denoting the maths test marks.

So X follows the normal distribution with

mean = = 70

and standard deviation = = 5

Let K be Stacey's actual score

Since Stacey's results were reported to be at the 95th percentile

But from the normal distribution table

So

So K = 78.225 78

So Stacey's actual score is 78.

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