statistics

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a study of 40 professors showed they spent on average 13.6 minutes correcting a student papers. Given a standard deviation of 17, the 90% confidence interval of the mean time for all the test papers is what?

  • statistics -

    Formula:
    CI90 = mean + or - 1.645(sd/√n)

    With your data:
    CI90 = 13.6 + or - 1.645(17/√40)

    I'll let you take it from here.

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