Statistics 250

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Final averages are typically approximately normally distributed with a mean of 65 and a standard deviation of 8. Your professor says that the top 10% of the class will receive an A; the next 20%, a B; the next 41%, a C; the next 19%, a D; and the bottom 10%, an F. (Give your answers correct to one decimal place.)

(a) What average must you exceed to obtain an A?


(b) What average must you exceed to receive a grade of C or better?


(c) What average must you obtain to pass the course? (You'll need a D or better.)

  • Statistics 250 -

    You need to learn how to use a normal probability distribution curve, or tables. There is one at
    http://psych.colorado.edu/~mcclella/java/normal/accurateNormal.html

    I used it to get the following answers:
    (a) A score = 75.3 or better
    (b) C score or higher (top 71%) = 60.8
    (c) Passing D score or higher (top 90%) = 54.7

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