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The next three questions refer to the following situation. Data from previous years reveal that the distribution if first exam scores in an introductory statistics class is approximately normal with a mean of 72 and a standard deviation of 12.

16) Given that the passing score is 65, approximately what percentage of students passes the first exam?

17) What is the probability that the student will score an “A” on the exam? (A score of 90 or more)

18) The middle 95% of the scores will tend to fall between _________ and ________.

  • Statistics -

    16. Z = (score-mean)/SD

    Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to to the Z score.

    17. Use same equation and table.

    18. Use table to find P = ± ,45 to get the two Z scores. Insert into equation above.

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