Â Â Â Â Records of 40 used passenger cars and 40 used pickup trucks were randomly sampled to investigate Â Â Â Â Â Â Â Â Â Â whether there...

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Â Â Â Â Records of 40 used passenger cars and 40used pickup trucks were randomly sampled to investigate
Â Â Â Â Â Â Â Â Â Â whetherthere was any significant difference in the mean time in years thatthey were kept by the original
Â Â Â Â Â Â Â Â Â Â ownerbefore being sold.Â Â For the sampled cars, the mean was5.3 years with a standard deviation of 2.2
Â Â Â Â Â Â Â Â Â Â years.Â Â Forthe sampled pickup trucks, the mean was 7.1 years with a standarddeviation of 3.0 years.Â Â
Â Â Â Â Â Â Â Â Â Â (Assumethat the two samples are independent.)
a)Â Â Construct and interpret the 90% confidenceinterval estimate of the difference between the mean time for allpassenger cars and the mean time for all pickup trucks.
b)Â Â Does there appear to be a significant differencebetween the two population means?Â Â Is one higher than
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â theother?Â Â If so, who keeps their vehicles longer?

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3.7 Ratings (622 Votes)

mean time for all passenger carsmean time for all pickup trucksGivenPassengers cars Sample 1Sample size n140Sample mean 53Sample standard deviation s122Pickup trucks Sample 2Sample size n240Sample mean 71Sample standard deviation s222for 90 confidence level 10090100010 2 0102 005aMethod 1Population Standard deviations not equal assumedFormula for Confidence Interval for Difference in two Populationmeans90 See Answer

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