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Chapter 8: Q. 8.18 (page 391)

Repeat part (a)of Problem8.2when it is known that the variance of a student’s test score is equal

to25.

Short Answer

Expert verified

Therefore,

P{X≥85}≤15=.2.

Step by step solution

01

Given Information.

the variance of a student’s test score is equal to25.

02

Explanation.

Let Xrepresents the test score of a student taking her final examination. Assume that Xis a random variable with mean μ=75and varianceσ2=25.

Then, using Corollarylocalid="1649833457509" 5.1. (textbook)a=10¯, we get:


localid="1650364326770" P{X≥85}=P{X≥75+10}≤σ2σ2+102=2525+100=15=0.2

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