Question

Based on tests of the Chevrolet Cobalt, engineers have found that the miles per gallon in highway driving are normally distributed, with a mean of 32 miles per gallon and a standard deviation of 3.5 miles per gallon.

a) If 25 cobalts are randomly selected, how many will have less than 30 miles per gallon?

b) How many miles per gallon determine the 3rd quartile?

c) 20 cobalts are randomly selecred and the miles per gallon for each car are recorded. What is the probabilty that the mean miles per gallon exceeds 31 miles per gallon?

Answer 1

Meen 32 U = ) std deviation , 03 3.5 ☺ P(x <3.) Plze 30-32 3.5 P(x2) P(22-0.57 P(x230) 2 0.2843 (using 2-table) pi o.2843 25 Expected No. 25 to 2843 7 about evill hove So less them 30 mpa quantle i 75th percentie 0.75 P( zar)= 0.75 he ?- Table using R620.674 Y - 32 0-674 3.5 X 34.36 mpf worl 3rd quritile i 34.36 mpa

ع) جلی =n ( ( 73 ) ( 7 ) 31- 3 3.S ال) متر (3.5 (( 21 ) = ( => - 1.238) ۱- (7- ۱۰ 38) : ((3(ة) } - أ { ( 23 ) = | - 0 . | 03 2(i>30) 0.4 Probability يع و 0.89