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Chapter 2: Q T2.9. (page 149)

The Environmental Protection Agency (EPA) requires that the exhaust of each model of motor vehicle be tested for the level of several pollutants. The level of oxides of nitrogen (NOX) in the exhaust of one light truck model was found to vary among individual trucks according to an approximately Normal distribution with mean μ=1.45 grams per mile driven and standard deviation σ=0.40 gram per mile. Which of the following best estimates the proportion of light trucks of this model with NOX levels greater than 2 grams per mile?

a.0.0228b.0.0846c.0.4256d.0.9154e.0.9772

Short Answer

Expert verified

The correct option is (b) 0.0846

Step by step solution

01

Given information

μ=1.45σ=0.40x=2

02

Concept

z=x−μσ

03

Calculation

z=x−μσ=2−1.450.40=1.375

P(x>2)=P(z>1.375)=1−P(z<1.375)=1−0.91545=0.08455

As a result, 0.0846 of this model's light trucks had a NOX level greater than 2 grams per mile.

Hence, the correct option is (b)

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