Chapter 10: Q 31. (page 643)
Let be the proportions of all college males and
females who worked last summer. The hypotheses to be tested are
a.
b.
c.
d.
e.
Option (a) is correct.
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A large toy company introduces many new toys to its product line each year. The
company wants to predict the demand as measured by y, first-year sales (in millions of dollars) using x, awareness of the product (as measured by the percent of customers who had heard of the product by the end of the second month after its introduction). A random sample of new products was taken, and a correlation of was computed. Which of the following is true?
a. The least-squares regression line accurately predicts first-year sales 96% of the time.
b. About of the time, the percent of people who have heard of the product by the end of the second month will correctly predict first-year sales.
c. About of first-year sales can be accounted for by the percent of people who have heard of the product by the end of the second month.
d. For each increase of 1% in awareness of the new product, the predicted sales will go up by million dollars.
e. About of the variation in first-year sales can be accounted for by the leastsquares regression line with the percent of people who have heard of the product by the end of the second month as the explanatory variable.
Which inference method?
a. A city planner wants to determine if there is convincing evidence of a difference in the average number of cars passing through two different intersections. He randomly selects times between a.m. and p.m., and he and his assistant count the number of cars passing through each intersection during the -minute interval that begins at that time.
b. Are more than of Toyota owners generally satisfied with their vehicles? Let’s design a study to find out. We’ll select a random sample of Toyota owners. Then we’ll ask each individual in the sample, “Would you say that you are generally satisfied with your Toyota vehicle?”
c. Are male college students more likely to binge drink than female college students? The Harvard School of Public Health surveys random samples of male and female undergraduates at four-year colleges and universities about whether they have engaged in binge drinking.
d. A bank wants to know which of two incentive plans will most increase the use of its credit cards and by how much. It offers each incentive to a group of current credit card customers, determined at random, and compares the amount charged during the following months.
Which inference method?
a. Drowning in bathtubs is a major cause of death in children less thanyears old. A random sample of parents was asked many questions related to bathtub safety. Overall,of the sample said they used baby bathtubs for infants. Estimate the percent of all parents of young children who use baby bathtubs.
b. How seriously do people view speeding in comparison with other annoying behaviors? A large random sample of adults was asked to rate a number of behaviors on a scale of(no problem at all) to(very severe problem). Do speeding drivers get a higher average rating than noisy neighbors?
c. You have data from interviews with a random sample of students who failed to graduate from a particular college inyears and also from a random sample of students who entered at the same time and did graduate withinyears. You will use these data to estimate the difference in the percent's of students from rural backgrounds among dropouts and graduates.
d. Do experienced computer-game players earn higher scores when they play with someone present to cheer them on or when they play alone? Fifty teenagers with experience playing a particular computer game have volunteered for a study. We randomly assign of them to play the game alone and the otherto play the game with a supporter present. Each player’s score is recorded.
National Park rangers keep data on the bears that inhabit their park. Here is a histogram of the weights of bears measured in a recent year:
Which of the following statements is correct?
a. The median will lie in the interval , and the mean will lie in the interval.
b. The median will lie in the interval, and the mean will lie in the interval
c. The median will lie in the interval and the mean will lie in the interval .
d. The mean will lie in the interval and the median will lie in the interval
e. The mean will lie in the interval and the median will lie in the interval .
Suppose the true proportion of people who use public transportation to get to work in the Washington, D.C. area is . In a simple random sample of people who work in Washington, about how far do you expect the sample proportion to be from the true proportion?
a.
b.
c.
d.
e.
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