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    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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    https://brainmass.com/statistics/percentile/finding-standard-scores-percentiles-509344

    Solution Preview

    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 ...

    Solution Summary

    The expert examines finding standard scores and percentiles.

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