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Suppose the scores on a certain midterm were not very high and their probability density function...

Suppose the scores on a certain midterm were not very high and their probability density function was ?(?) = 1 /14480 ⋅ (3? + 1), 20 ≤ ? ≤ 100.

a) What is the expected value of the scores, ?[?]?

b) What is the standard deviation of the scores, ??[?]?

c) What as the 90th percentile? i.e. Find c such that ?[? ≤ ?] = 0.9

Math   Statistics-And-Probability   
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