Exam 8: Regression, Associations, and Predictive Modeling

Over the trial month the rate of in-store sales rose to 30% of shoppers. The store's owner decided this increase was statistically significant. Now that she's convinced the mannequins work, why might she still choose not to purchase them?

A brake and muffler shop reported the repair bills, in dollars, for their customers yesterday. 88 283 312 290 172 154 400 381 346 181 203 118 143 252 227 56 192 292 213 422 a. Sketch a histogram for these data. b. Find the mean and standard deviation of the repair costs. c. Is it appropriate to use the mean and standard deviation to summarize these data? Explain. d. Describe the association of repair costs.

What is the probability that at least 5 of his first 50 customers buy magazines?

Which service contract should the restaurant expect to cost more each year? How much more? With what standard deviation?

The owner talked the salesman into extending the trial period so that she can base her decision on data for a full month. Will the power of the test increase, decrease, or remain the same?

The student insists to his media teacher at school that movie attendance is on the rise. Do you agree with this conclusion?

If the monkeys enjoy this activity every night for an entire week, what are the chances that a monkey falls off the bed every one of the seven nights?

Do you think mode of transportation is independent of gender? Give statistical evidence to support your conclusion.

The model $\sqrt { \hat { s t r } } = 12 + 20 \text { dia }$ can be used to predict the breaking strength of a rope (in pounds) from Its diameter (in inches). According to this model, how much force should a rope one-half inch in Diameter be able to withstand?

Describe how to use a prospective study to determine if the home teams have an unfair advantage when shooting free-throws.

Does this sample provide evidence that people are attending the movies more often? Provide a complete significance test to support your answer.

What is the probability that the first two customers both get a 50% discount?

A researcher found that a 98% confidence interval for the mean hours per week spent studying by College students was (13, 17). Which is true? I. There is a 98% chance that the mean hours per week spent studying by college students is Between 13 and 17 hours. II. 98% of college students study between 13 and 17 hours a week. III. Students average between 13 and 17 hours per week studying on 98% of the weeks.

Roadblocks From time to time police set up roadblocks to check cars to see if the safety inspection is up to date. At one such roadblock they issued tickets for expired inspection stickers to 22 of 628 cars they stopped. a. Based on the results at this roadblock, construct and interpret a 95% confidence interval for the proportion of autos in that region whose safety inspections have expired. b. Explain the meaning of "95% confidence" in part a).

The SPCA has kept these data records for the past 20 years. If they want to show the trend in the Number of dogs they have housed, what kind of plot should they make?

In this context describe a Type I error and the impact such an error would have on the store.

A certain population is bimodal. We want to estimate its mean, so we will collect a sample. Which Should be true if we use a large sample rather than a small one? I. The distribution of our sample data will be more clearly bimodal. II. The sampling distribution of the sample means will be approximately normal. III. The variability of the sample means will be smaller.

Assuming the owner is correct in thinking that 5% of the customers purchase magazines, how many customers should he expect before someone buys a magazine?

Truckers On many highways state police officers conduct inspections of driving logbooks from large trucks to see if the trucker has driven too many hours in a day. At one truck inspection station they issued citations to 49 of 348 truckers that they reviewed. a. Based on the results of this inspection station, construct and interpret a 95% confidence interval for the proportion of truck drivers that have driven too many hours in a day. b. Explain the meaning of "95% confidence" in part A.

Which of these random variables is most likely to have a binomial model?