10.9

a.Assuming that the population variances from both office are equal,is there evidence of a difference in the mean waiting time between the two office? (use α = 0.05.)

b. Find the *P *value in (a) and interpret its meaning.

c. What other assumption in necesarry in (a) ?

d. Assuming that the population variances from both office are equal, construct and interpret a 95% confidence interval estimate of the difference between the population means in the two office.

10.11

An impportant feature of digital cameras is battery life, the number of shots that can be taken before the battery needs to be recharge. The file DigitalCameras contains the battery life of 29 subcompact cameras and 16 compact cameras. (Data extracted from “Digital Cameras”, Consumer Reports, July 2009, pp.28-29.)

a. Assuming that the population variances from both types of digital cameras are equal, is there evidence of a difference in the mean battery life between the two types of digital cameras (α = 0.05) ?

b. Determine the *P *value in (a) and interpret its meaning.

c. Assuming that the population variances from both of types of digital cameras are equal, construct and interpret a 95% confidence interval estimate of the difference between the population mean battery life of the two types of digital cameras.

10.21

In Industial setting, alternative methods often exist for measuring variable of interest. The data in Measurement ( codet to maintain confidentiality) represent measurements in-line that were colected from an analizer during the production procces and from an anilitical lab. ( Data extracted from M.Leitnaker, “Comparing Measurement Processes: In-Line Versus Analitical Measurement”, Quality Engineering, 13, 2000-2001, pp. 293-398.)

a. At the 0.05 levelof significance, is there evidence of a difference in the mean of measurement in-line and form an analitical lab?

b. What assumption in a necessary about a population distribution in order to perform this test?

c. Use a grapichal method to evaluate the Validity of the assumption in (a).

d. Construct and interpret a 95% confidence interval estimate of the difference in the mean measuremens in-line and form an analitical lab.

10.23

In tought economic times, the bussiness staff at magazines are challengged to sell advertising space in their publication. Thus, one indicator of a week economy is the decline in the number of “ad pages” that magazine have sold. The file ad page contains the number of ad pages found in the May 2008 an May 2009 issues of 12 men’s magazine. (Data extracted from W.Levith, magazine monitor, media week, April 20, 2009, p. 53)

a. At the 0.05 levelof significance, is there evidence that the mean number of ad pages was higher in May 2009?

b. What assumption in a necessary about a population distribution in order to perform this test?

c. Use a grapichal method to evaluate the Validity of the assumption in (b).

d. Construct and interpret a 95% confidence interval estimate of the difference in the mean number of ad pages in men’s magazine between May 2008 and May 2009?

10.48

An impportant feature of digital cameras is battery life, the number of shots that can be taken before the battery needs to be recharge. The file DigitalCameras contains the battery life of 29 subcompact cameras and 16 compact cameras. (Data extracted from “Digital Cameras”, Consumer Reports, July 2009, pp.28-29.)

a. Is there evidence of a difference in the variability of the battery life between the two types of digital cameras? (use α = 0.05.)

b. Determine the *P *value in (a) and interpret its meaning.

c. What assumption about the population distribution of the two types of cameras in necessary in (a)? is the assumption valid for these data?

d. Based on the result of (a), which *t *test defined in section 10.1 should yo use the to compare the mean battery life of the two types of cameras?