Exam 8: Regression, Associations, and Predictive Modeling

Surprised by the low number of Type B blood donors at the blood drive, the American Red Cross wonders if the 11% estimate was too high for your area. How many Type B blood donors would it take to convince you that this estimate might be too high? Justify your answer.

Residuals are . . .

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

Can watching a movie temporarily raise your pulse rate? Researchers have 50 volunteers check Their pulse rates. Then they watch an action film, after which they take check their pulse rates once More. Which aspect of experimentation is present in this research?

During a budget meeting, local school board members decided to review class size information to determine if budgets were correct. Summary statistics are shown in the table. 33.39 students s 5.66 students min 17 Q1 29 median 33 Q3 40 max 40 a. Notice that the third quartile and maximum class sizes are the same. Explain how this can be. b. The school district declares that classes with enrollments fewer than 20 students are "too small". Would you consider a class of 20 students to be unusually small? Explain. c. The school district sets the office supply budgets of their high schools on the enrollment of students. The district budgets each class $12 plus $0.75 per student, so a class with one student receives $12.75 and the classes with 40 students rec $12 + 0.75 ( 40 ) = \$ 42$ . What is the median class budget for office supplies? And the IQR? d. What are the mean and standard deviation of the class office supply budgets?

What alpha level did the group use?

Although there are annual ups and downs, over the long run, growth in the stock market averages About 9% per year. A model that best describes the value of a stock portfolio is probably:

Design an experiment to determine whether the diet and exercise programs are effective in helping dogs to lose weight.

Do you think there is a pattern? Describe the association between speed and the number of strikeouts.

Poverty In a study of how the burden of poverty varies among U. S. regions, a random sample of 1000 individuals from each region of the United States recently yielded the information on poverty (based on defining the poverty level as an income below $10,400 for a family of 4 people). The data and calculation of the test statistic is shown in the table below. (All the conditions are satisfied - don'ft worry about checking them.) = 0.67+2.12+9.00+0.53+ 12.31+ 0.09+0.29+1.24+0.07+ 1.70 =14.01 P=0.0029 a. Write appropriate hypotheses. b. Suppose the expected values had not been given. Show exactly how to calculate the expected count in the first cell. c. How many degrees of freedom are there? d. State your complete conclusion in context.

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

A philosophy professor wants to find out whether the mean age of the men in his large lecture class Is equal to the mean age of the women in his classes. After collecting data from a random sample of His students, the professor tested the hypothesis H0: µM - µW = 0 against the alternative HA: µM ΜW ≠ 0. The P-value for the test was 0.003. Which is true?

Herpetologists (snake specialists) found that a certain species of reticulated python have an average length of 20.5 feet with a standard deviation of 2.3 feet. The scientists collect a random sample of 30 adult pythons and measure their lengths. In their sample the mean length was 19.5 feet long. One of the herpetologists fears that pollution might be affecting the natural growth of the pythons. Do you think this sample result is unusually small? Explain.

What is the predicted number of skiers for a Saturday with a temperature of 40° F. and a snow cover of 25 inches?

Make a scatterplot and describe the association between the year and the first class postal rate.

Should the representatives from the Department of Labor conclude that the percentage of females in their labor force is lower than Europe's rate of 46%? Explain.

Researchers studying growth patterns of children collect data on the heights of fathers and sons. The correlation between the fathers' heights and the heights of their 16 year-old sons is most likely To be . . .

Associations For each pair of variables, indicate what association you expect: positive linear(+), negative linear(-), curved(C), or none(N). a. the number of miles a student lives from school; the student's GPA b. a person's blood alcohol level; time it takes the person to solve a maze c. weekly sales of hot chocolate at a Montana diner; the number of auto accidents that week in that town d. the price charged for fund-raising candy bars; number of candy bars sold e. the amount of rainfall during growing season; the crop yield (bushels per acre)

Which of these random variables has a binomial model?

R-sq is a measure of ...