We perform a statistical test to examine if the mean amount filled of soft drinks has increased when cans are filled by a new machine compared to the old machine. Which of the following is a Type II error?

a. Conclude that the new machine did not increase the mean amount filled when in fact it does.

b. Conclude that the new machine did not increase the mean amount filled when in fact it does not.

c. Conclude that the new machine increased the mean amount filled when in fact it does.

d. Conclude that the new machine increased the mean amount filled when in fact it does not.

A researcher reports that a test is "significant at 5%." This test will be

a. not significant at 1%.

b. significant at 10%.

c. significant at 1%.

A researcher wants to know if the average time in jail for robbery has increased from what it was several years ago when the average sentence was 7 years. He obtains data on 400 more recent robberies and finds an average time served of 7.5 years. If we assume the standard deviation is 3 years, a 95% confidence interval for the average time served is

a. (7.21, 7.79)

b. (7.25, 7.75)

c. (7.11, 7.89)