On the SAT, the average Writing score is 477 points and the average Mathematics

Question

On the SAT, the average Writing score is 477 points and the average Mathematics score is 552 points. The standard deviation is 84 points on each part of the test. Now suppose 37 test takers are selected. (See exercise 21 on page 326 of your textbook for a similar problem.) Question 4 92% of the time the sample average writing score should be less than what? (Remember the label). The time it takes to bake a Betty Crocker Supermoist Fudge Cake is normally distributed with a mean of 44 minutes and a variance of 32 minutes*2. Let baking time, in minutes, be represented by random variable X. Question 5 P(x1

Explanation / Answer

4) for 93 percentile z =1.4051

std error of mean =std deviation/(n)1/2 =84/(37)1/2 =13.8095

therefore correspodning value =mean +z*std error =477+1.4051*13.8095=496.4034

5) std deviation =(32)1/2 =5.657

P(x1<X<49) =0.1180

P((x1-44)/5.657<Z<(49-44)/5.657)=0.1180

P((x1-44)/5.657<Z<0.8839)=0.1180

0.8116 -(P((x1-44)/5.657<Z)=0.1180

(P((x1-44)/5.657<Z) =0.6936

(x1-44)/5.657)=0.5061

x1 =0.5061*5.657+44 =46.8632

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