Stats 250 W16 Final Exam Review April 19

Stats 250 W16 Final Exam Review April 19 - Stats 250 Winter...

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Stats 250 Winter 2016: Final Exam Review 1. Unusual Average Score or Not? Scores for incoming students on a placement exam are modeled with a normal distribution having a mean of 100 points and a standard deviation of 10 points. How likely would it be to see an average score of 110 points or higher for a random sample of 4 such incoming students? Show all work. 2. Response Accuracy – The accuracy of verbal responses is tested in an experiment in which a random sample of adults are first asked to report their height and then their actual height is measured (both in inches). The data will be used to assess if adults tend to report they are taller than they really are, on average, using a 5% significance level. For each adult the two heights were compared as Reported Height less Actual Height (i.e., Reported Height – Actual Height). a. State the hypotheses for assessing if adults tend to report they are taller than they really are on average. H 0 : ____________________________________ versus H a : _________________________________________ b. Suppose that the sample mean difference ( Reported Height – Actual Height ) was 1.38 standard errors above 0. Report the corresponding test statistic (include its symbol and value). Test statistic: _________ = ______________________ c. The results were not statistically significant at the 5% level. Write an appropriate statistical decision and conclusion in context. d. The researcher remembers that there are assumptions for any test, to ensure its integrity. She believes the adults that participated in the study are representative of the population and can be treated as a random sample; but because her sample size was small, there is an additional assumption. Clearly state that assumption in context.
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3 . Healthy Grocery Shopping Four public health graduate students from UM created a start-up company to increase access to healthy foods by coordinating rides to and from well-stocked grocery stores. Last month, they piloted this idea to a name brand grocery store and provided rides for people in two cities: 1 = Highland Park and 2 = Detroit. They measured a number of outcomes, including cost of the coordinated ride for the customer, number of items purchased, and amount of money spent at the store on groceries. The graduate students would like to estimate the difference in the two population mean costs of the ride ( Highland Park (1) Detroit (2) ) using a 95% confidence interval. Data for the cost for the 29 Highland Park customers and the 17 Detroit customers were first summarized using R.
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