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Nine students took the SAT. Their scores are listed below. Later on, they read a book on test preparation and retook the SAT. Their new scores are listed below. Construct a 95% confidence interval for µ d (the true mean difference in scores). Assume that the distribution is normally distributed.

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    Where are the scores

  • statistics -

    Find the mean first = sum of scores/number of scores

    Subtract each of the scores from the mean and square each difference. Find the sum of these squares. Divide that by the number of scores to get variance.

    Standard deviation = square root of variance

    95% = mean ± 1.96 SEm

    SEm = SD/√n

    You can do the calculations.

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