Suppose adults in a particular sleep 8 hours a night with a standard deviation o

Question

Suppose adults in a particular sleep 8 hours a night with a standard deviation of 5 hours. Using the normal curve table. a. What percentage of adults sleep below 7.4 hours? b. What percentage of adults sleep below 6.8 hours or above 8.1 hours? c. What percentage of adult sleep between 7.5 and 8.4 hours? d. How many hours does someone need to sleep to be included in the top 10%? e. How many hours does someone need to sleep to drive to be included in the bottom 25% f. Explain your answer to a person who is familiar with mean, standard deviation, and 2 scores, but not with normal curve percentages.

Explanation / Answer

sol

mean=8

sd=5

solutiona:

P(x<7.4)

z=x-mean/sd

=7.4-8/5

=-0.6/5

=-0.12

P(Z<-0.12) to be found

P(Z<-0.12) =1-P(Z<0.12)

=1-0.5478

=0.4522

ANSWER

0.4522*100=45.22%

Solutionc:

P(7.5<x<8.4)

P(7.5-8/5<z<8.4-8/5)

=P(-0.5/5<z<0.08)

=P(-0.1<Z<0.08)

=0.0717

answer 0.0717*100=7.17%

=7.17%

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