Chapter 18: Inferences about Means
Suppose I want to test whether students' textbook costs for this semester are higher on average than the average cost of $450 in 2000. What would be an appropriate alternative hypothesis? Choose the correct answer below. A. μ ≠450 B. μ >450 C. μ <450 D. x overbar >450
B. μ >450
A student on the track team wants to test whether her times to run a mile are different after a new training regimen. Previously, her average time to run a mile was 8 minutes. Which is an appropriate alternative hypothesis? Choose the correct answer below. A. μ >8 B. μ<8 C. μ ≠8 D. x overbar <8
C. μ ≠8
Suppose we are making a 95% confidence interval for the population mean from a sample of size 15. What number of degrees of freedom should we use? a. 14 b. 16 c. 15 d. there is not enough information given to find out
a. 14
Which of the following statements is true about the family of t distributions? a. t distributions are symmetric and unimodal b. t distributions have fatter tails and narrower centers than Normal models c. As the degrees of freedom increase, the t distributions approach the Normal distribution
all are true
Suppose we construct a 90% confidence interval for a mean. This is equivalent to a two-tailed hypothesis test with _______ level of significance. a. 5% b. 10% c. 1% d. 20%
b. 10%
Which of the following is not a condition to check to estimate the mean of a population? Choose the correct answer below. A. The sample is no more than 10% of the population. B. Data are randomly gathered. C. There are at least 10 successes and 10 failures in the sample. Your answer is correct. D. The data come from a population that is unimodal and symmetric.
c. There are at least 10 successes and 10 failures in the sample
On a final project in an introductory statistics class, a student reports a 95% confidence interval for the average cost of a haircut to be ($5.50,$65.00). What is the correct interpretation of this confidence interval? a. 95% of the sample falls between these two values. b. There is 95% confidence that the sample mean is between these two values c. There is 95% confidence that the population mean is between these two numbers
c. There is 95% confidence that the population mean is between these two numbers
Suppose we want to estimate the proportion of defective items produced by a manufacturing process. Could we use the methods of this chapter to answer this question? yes/ no
no