Exam 8: Regression, Associations, and Predictive Modeling

What are the mean and standard deviation for the profit on a 1000 plans?

Dimes minted in the United States average 2.286 g with a standard deviation of 0.06 g. Nickels have a mean of 5.000 g and a standard deviation of about 0.08 g. A couple chemistry students were trying out their teacher's new scale by weighing a bunch of coins. They found a nickel that weighed 5.19 g and a dime that weighed 2.45 g. Which coin was more exceptionally heavy? Explain.

The admissions officers want to estimate the true percentage of private school applicants to within $\pm 4 \% \text {, with } 90 \%$ onfidence. How many applications should they sample?

All but one of the statements below contain a mistake. Which one could be true?

Consider the following part of a data set: Age (years) Sex Only child? Height (inches) Weight (pounds) Credit Hours GPA Major 21 Female Yes 67.00 140.0 16 3.60 animal science 20 Female No 62.00 130.0 18 3.86 biology 28 Female No 64.00 188.0 21 3.25 psychology 21 Male No 65.00 140.0 15 2.95 psychology 24 Female No 67.00 130.0 20 3.00 anthropology 22 Male Yes 68.00 135.0 15 2.94 journalism List the variables in the data set. Indicate whether each variable is treated as categorical or quantitative in this data set. If the variable is quantitative, state the units.

Medical records indicate that people with more education tend to live longer; the correlation is 0.48. The slope of the linear model that predicts lifespan from years of education suggests that on average People tend to live 0.8 extra years for each additional year of education they have. The slope of the Line that would predict years of education from lifespan is

We want to know the mean winning score at the US Open golf championship. An internet search Gives us all the scores for the history of that tournament, and we create a 95% confidence interval Based on a t-distribution. This procedure was not appropriate. Why?

Compare the two distributions of the women's heights. Be sure to talk about shape, center, and spread.

An online catalog company wants on-time delivery for at least 90% of the orders they ship. They Have been shipping orders via UPS and FedEx but will switch to a more expensive service (ShipFast) if there is evidence that this service can exceed the 90% on-time goal. As a test the Company sends a random sample of orders via ShipFast, and then makes follow-up phone calls to See if these orders arrived on time. Which hypotheses should they test?

Carry out the appropriate test and state your conclusion in context.

The following is a scatterplot of the average final exam score versus midterm score for 11 sections of an introductory statistics class: The correlation coefficient for these data is $r = 0.829$ 29. If you had a scatterplot of the final exam score versus midterm score for all individual students in this introductory statistics course, would the correlation coefficient be weaker, stronger, or about the same? Explain.

What is the probability that the tenth blood donor is the first donor with Type B blood?

Test an appropriate hypothesis and state your conclusion.

Describe to the group an advantage and a disadvantage of using an alpha level of 5% instead.

Luxury cars According to infoplease, 18.8% of the luxury cars manufactured in 2003 were silver. A large car dealership typically sells 50 luxury cars a month. a. Explain why you think that the luxury car sales can be considered Bernoulli trials. b. What is the probability that the fifth luxury car sold is the first silver one? c. Let X represent the number of silver luxury cars sold in a typical month. What is the probability model for X? Specify the model (name and parameters), and tell the mean and standard deviation.

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

For purposes of making on-campus housing assignments, a college classifies its students as Priority A (seniors), Priority B (juniors), and Priority C (freshmen and sophomores). Of the students who choose to live on campus, 10% are seniors, 20% are juniors, and the rest are underclassmen. The most desirable dorm is the newly constructed Gold dorm, and 60% of the seniors elect to live there. 15% of the juniors also live there, along with only 5% of the freshmen and sophomores. What is the probability that a randomly selected resident of the Gold dorm is a senior? Show your work clearly on the back of this page.

Which is true about a 98% confidence interval for a population proportion based on a given Sample? I. We are 98% confident that other sample proportions will be in our interval. II. There is a 98% chance that our interval contains the population proportion. III. The interval is wider than a 95% confidence interval would be.

AP Grading Every year Educational Testing Services (ETS) selects graders for the Advanced Placement (AP) Exams. Recently the AP Statistics exam has been graded in Lincoln, Nebraska. One objective of ETS is to have consistent grading by inviting graders from all over the nation. However travel expenses are an issue. The accountants at ETS wonder if the flight costs from cities west of Lincoln are the same as flight costs from cities east of Lincoln. A random sample of the expense vouchers from last year was reviewed for the cost of airline tickets. The data are shown in the table below. Indicate what inference procedure you would use to see if there is a significant difference in the costs of airline flights to Lincoln from the west and from the east, then decide if it is okay to actually perform that inference procedure. (Check the appropriate assumptions and conditions and indicate whether you could or could not proceed. You do not have to do the actual test.) Cost from east Costs from west 265 257 298 320 340 295 219 288 199 366 398 275 359 430 309 397 105 253 253 366

Explain what 95% confidence means in this context.