# Finding standard scores and percentiles

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A set of 50 data values has a mean of 15 and a variance of 25. Find the standard score of a data value = 30.

Following are the American College Test (ACT) scores attained by the 25 members of a local high school graduating class:

21 24 23 17 31 19 19 20 19 25 17 23 16

21 20 28 25 25 21 14 19 17 18 28 20

Find P99, P90, and P80 for the ACT scores. [Hint: Use nk/100 to find the location in the ordered data for each percentile.]

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Hi there,

Thanks for selecting me as your expert. Here is my explanation:

1. The formula we use to calculate the standard score (or z score) is z=(x-mean)/sd.

Based ...

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The expert examines finding standard scores and percentiles.

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