statistics question: an auto parts company advertises that its special oil additive will make the engine run smoother, cleaner, longer, with fewer repairs. an independent laboratory decides to test part of this claim. it arranges to use a taxicab company‘s fleet of cars. the cars are randomly divided into 2 groups. the companys mechanics will use the additive in one group of cars but not in the other. at the end of a year the laboratory will compare the percentage of cars in each group that required engine repairs.a) what kind of a study is this?b) will they do a one- tailed or a two-tailed test?c) if the cabs with the additive do indeed run significantly better, can the company conclude it is an effect of the additive? can they generalize this result and recommend the additive for all cars? explain
ro a) what kind of a study is this? 2-Proportion Z-Test b) will they do a one- tailed or a two-tailed test? This is a 1-tailed test since the researchers are expecting the additive to produce a lower percentage of repairs. p2 p1 If it was a 2-tailed test, the researchers would only want to see that the percentage of repairs between the two samples are different, but not necessarily higher or lower. p2 ≠ p1 c) if the cabs with the additive do indeed run significantly better, can the company conclude it is an effect of the additive? There is always a possibility of confounding influences. For example, it does not say that this is a double-blind test where neither the taxi drivers or the researchers are unaware which cars have the additives. It will be in the researchers advantage if they can influence the results because it will benefit them financially. can they generalize this result and recommend the additive for all cars? explain Not really, since not all cars are put through the amount of driving a taxicab goes through. For example, a grandma who only drives to church on Sunday would not likely see any benefit. Hope that helps
