statistics

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If a large number of people guess randomly on each of 100 items on a true-false test, the mean would be expected to be ì=___*, and ó=__*.

What % of the examinees would be expected to get a score of 65 or >?

  • statistics -

    The mean is p*N = 50
    where p is the probability of getting gthe correct answqer by guessing at random. N is the number of tosses

    The variance is p(1 -p)N = 25

    The standard deviation is
    ó = sqrt25 = 5.

    Use a normal ditributuion curve for the probability of getting a score of 65 or better. You are talking 3 sigma from the mean.

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