BUSINESS BUS-352- Assuming that the population variances from both types of tablets are equal

10.11 An important feature of tablets is battery life, the number
of hours before the battery needs to be recharged. The file Tablets
contains the battery life of 12 WiFi-only and 7 3G/4G/WiFi
9- through 12-inch tablets. (Data extracted from “Ratings and recommendations:
Tablets,” Consumer Reports, August 2013, p. 24.)

a. Assuming that the population variances from both types of
tablets are equal, is there evidence of a difference in the mean
battery life between the two types of tablets? 1Use a = 0.05.2

b. Determine the p-value in (a) and interpret its meaning.

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

10.17 Brand valuations are critical to CEOs, financial and
marketing executives, security analysts, institutional investors,
and others who depend on well-researched, reliable information
needed for assessments, and comparisons in decision making.
Millward Brown Optimor has developed the BrandZ Top 100
Most Valuable Global Brands for WPP, the world’s largest communications
services group. Unlike other studies, the BrandZ Top
100 Most Valuable Global Brands fuses consumer measures of
brand equity with financial measures to place a financial value on
brands. The file BrandZTechFin contains the brand values for two
sectors in the BrandZ Top 100 Most Valuable Global Brands for
2014: the technology sector and the financial institutions sector.
(Data extracted from bit.ly/18OL5Mu.)

a. Assuming that the population variances are equal, is there evidence
of a difference between the technology sector and the
financial institutions sector with respect to mean brand value?
(Use a = .05.)

b. Repeat (a), assuming that the population variances are not equal.

c. Compare the results of (a) and (b).

10.23 What motivates employees? The Great Place to Work
Institute evaluated nonfinancial factors both globally and in the
United States. (Data extracted from L. Petrecca, “Tech Companies
Top List of ‘Great Workplaces,’” USA Today, October 31, 2011,
p. 7B.) The results, which indicate the importance rating of each
factor, are stored in Motivation .

a. At the 0.05 level of significance, is there evidence of a difference
in the mean rating between global and U.S. employees?

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

c. Use a graphical method to evaluate the validity of the assumption
in (b).

10.45 A problem with a telephone line that prevents a customer
from receiving or making calls is upsetting to both the customer
and the telecommunications company. The file Phone contains
samples of 20 problems reported to two different offices of a telecommunications
company and the time to clear these problems (in
minutes) from the customers’ lines.

a. At the 0.05 level of significance, is there evidence of a difference
in the variability of the time to clear problems between the
two central offices?

b. Determine the p-value in (a) and interpret its meaning.

c. What assumption do you need to make in (a) about the two
populations in order to justify your use of the F test?

d. Based on the results of (a) and (b), which t test defined in Section
10.1 should you use to compare the mean time to clear
problems in the two central offices?