stat 11 hw

stat 11 hw - Stat 101-002 Heller Cengiz Rahmioglu Penn ID...

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Stat 101-002 Cengiz Rahmioglu Heller Penn ID: 37479511 STAT 101 HW 1. a) Four-wheel drive models command a different price as used cars than two-wheel drive models on average. When we do a two-sample t-test for the difference in means, the t- statistic is found to be 3.1. As t>=2, we can conclude that the two samples are statistically significantly different from each other. p-value < 0.05 so reject H 0 hypothesis. b) The 95% confidence interval for the difference in prices is [$619, $2779] which means that we are 95% confident that the average price difference between four-wheel and two-wheel models lies between $619 and $2779. As the interval doesn’t include 0, we can conclude that the two sample means are statistically different from each other which verifies our statement in part a). c) Yes on average four-wheel drive models are $1699 more expensive with a standard error of $547. The price differential is probably caused by se (y 2 -y 1 )) the difference in the production costs of the 4-wheel drive model and the 2-wheel drive model. (z=1699/546.8=3.1 P(Z>3.1)=0.0023<0.05 reject H 0 .) d) The age of the car is a confounding factor. If the 4-wheel drive models used in this experiment are relatively newer than the 2-wheel drive models, then the difference in the prices may be caused by the age difference rather than the models. As this is a lurking facto, our answer in c) is probably wrong. 2.
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This note was uploaded on 06/22/2008 for the course STAT 101 taught by Professor Heller during the Fall '08 term at UPenn.

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stat 11 hw - Stat 101-002 Heller Cengiz Rahmioglu Penn ID...

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