# Question

A random sample of 25 items is drawn from a population whose standard deviation is unknown. The sample mean is x-bar = 850 and the sample standard deviation is s = 15. Use Appendix D to find the values of Student's t.

a. Construct an interval estimate of with 95 percent confidence.

b. Repeat part a assuming that s = 30.

c. Repeat part a assuming that s = 60.

d. Describe how the confidence interval changes as s increases.

a. Construct an interval estimate of with 95 percent confidence.

b. Repeat part a assuming that s = 30.

c. Repeat part a assuming that s = 60.

d. Describe how the confidence interval changes as s increases.

## Answer to relevant Questions

A sample of 21 minivan electrical warranty repairs for "loose, not attached" wires (one of several electrical failure categories the dealership mechanic can select) showed a mean repair cost of $45.66 with a standard ...Calculate the standard error of the sample proportion. a. n = 30, π = .50 b. n = 50, π = .20 c. n = 100, π = .10 d. n = 500, π = .005 Of 43 bank customers depositing a check, 18 received some cash back. (a) Construct a 90 percent confidence interval for the proportion of all depositors who ask for cash back. (b) Check the normality assumption of p. A random survey of 500 students was conducted from a population of 2,300 students to estimate the proportion who had part-time jobs. The sample showed that 245 had part-time jobs. Calculate the 90 percent confidence interval ...What sample size would be required to estimate the true proportion of American female business executives who prefer the title "Ms.," with an error of ±0.025 and 98 percent confidence?Post your question

0