Question 1:

A researcher is interested in estimating the mean value for a population. She takes a random sample of 17 items and computes a sample mean of 224 and a sample standard deviation of 32. She decides to construct a 98% confidence interval to estimate the mean. The degrees of freedom associated with this problem are _______.

a)18

b)17

c)16

d)15

1.2Use Table 4 Critical Values of the Student t Distribution (Appendix B-10) to determine the t- value for a two-tailed hypothesis test in which a null hypothesis about a population mean is tested at the 5% level of significance based on one sample with a sample size of 13. Assume that the population variance is unknown.

a)1.782

b)2.179

c)2.681

d)3.055

1.3Consider the following null and alternative hypotheses:

Ho: =67 H1:<67

These hypotheses _______________.

a) indicate a one-tailed test with a rejection area in the right tail

b) indicate a one-tailed test with a rejection area in the left tail

c) indicateatwo-tailedtest

d) are established incorrectly

1.4A sample of 81 account balances of a credit company showed an average balance of $1,200 with a standard deviation of $126. Which of the following hypotheses can be used to determine whether the mean of all account balances is significantly different from $1,150?

a) H0:= 1150 H1:>1150

b) H0:=1150 H1:<1150

c) H0:= 1150 H1:=/ 1 1 5 0

d) H0:=/ 1150 H1:=1150

1.5 Assuming the same sample size and the same standard deviation, a 90% confidence interval will be ___ than a 95% confidence interval.

a)wider

b)narrower

c)equal to

d)cannot tell