statistics

50 question multiple choices with A, B, C, D

Probability of an unsual score?

Probability of between 20 and 30 correct inclusive?

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  1. I assume you want the probability of getting 20 to 30 right by random guessing of answers. The mean value will be 1/4 x 50 = 12.5 and the standard deviation will be sqrt (.25*.75*50) = 3.1
    Using the normal distribution Java tool at this website,
    http://psych.colorado.edu/%7Emcclella/java/normal/accurateNormal.html ,
    I get the probability of 20 to 30 correct answers to be 0.78%

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