Ch. 10 Part I

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10.7

10.7 When people make estimates, they are influenced by anchors
to their estimates. A study was conducted in which students were
asked to estimate the number of calories in a cheeseburger. One group
was asked to do this after thinking about a calorie-laden cheesecake.
A second group was asked to do this after thinking about an organic
fruit salad. The mean number of calories estimated in a cheeseburger
was 780 for the group that thought about the cheesecake and 1,041 for
the group that thought about the organic fruit salad. (Data extracted
from “Drilling Down, Sizing Up a Cheeseburger’s Caloric Heft,” The
New York Times, October 4, 2010, p. B2.) Suppose that the study was
based on a sample of 20 people who thought about the cheesecake
first and 20 people who thought about the organic fruit salad first, and
the standard deviation of the number of calories in the cheeseburger
was 128 for the people who thought about the cheesecake first and
140 for the people who thought about the organic fruit salad first.
a. State the null and alternative hypotheses if you want to determine
whether the mean estimated number of calories in the cheeseburger
is lower for the people who thought about the cheesecake first than
for the people who thought about the organic fruit salad first.
b. In the context of this study, what is the meaning of the Type I
error?
c. In the context of this study, what is the meaning of the Type II
error?
d. At the 0.01 level of significance, is there evidence that the
mean estimated number of calories in the cheeseburger is lower
for the people who thought about the cheesecake first than for
the people who thought about the organic fruit salad first?

10.17

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).

10.20

10.20 Nine experts rated two brands of Colombian
coffee in a taste-testing experiment. A rating on a
7-point scale (1 = extremely unpleasing, 7 = extremely pleasing)
is given for each of four characteristics: taste, aroma, richness,
and acidity. The following
data stored in Coffee contain the
ratings accumulated over all four characteristics:
a. At the 0.05 level of significance, is there evidence of a difference
in the mean ratings between the two brands?
b. What assumption is necessary about the population distribution
in order to perform this test?
c. Determine the p-value in (a) and interpret its meaning.
d. Construct and interpret a 95% confidence interval estimate of
the difference in the mean ratings between the two brands.

10.34

10.34 Does co-browsing have positive effects on the customer
experience? Co-browsing refers to the ability to have a contact
center agent and customer jointly navigate an online document or
mobile application on a real-time basis through the web. A study
of businesses indicates that 81 of 129 co-browsing organizations
use skills-based routing to match the caller with the right agent,
whereas 65 of 176 non-co-browsing organizations use skills-based
routing to match the caller with the right agent. (Source: Cobrowsing
Presents a ‘Lucrative’ Customer Service Opportunity, available at
bit.ly/1wwALWr.)
a. At the 0.05 level of significance, is there evidence of a difference
between co-browsing organizations and non-co-browsing
organizations in the proportion that use skills-based routing to
match the caller with the right agent?
b. Find the p-value in (a) and interpret its meaning.

10.47

10.47 A bank with a branch located in a commercial district of a
city has the business objective of improving the process for serving
customers during the noon-to-1 p.m. lunch period. To do so,
the waiting time (defined as the number of minutes that elapses
from when the customer enters the line until he or she reaches the
teller window) needs to be shortened to increase customer satisfaction.
A random sample of 15 customers is selected and the
waiting times are collected and stored in Bank1 . These data are:
4.21 5.55 3.02 5.13 4.77 2.34 3.54 3.20
4.50 6.10 0.38 5.12 6.46 6.19 3.79
Suppose that another branch, located in a residential area, is also
concerned with the noon-to-1 p.m. lunch period. A random sample
of 15 customers is selected and the waiting times are collected and
stored in Bank2 . These data are:
9.66 5.90 8.02 5.79 8.73 3.82 8.01 8.35
10.49 6.68 5.64 4.08 6.17 9.91 5.47
a. Is there evidence of a difference in the variability of the waiting
time between the two branches? (Use a = 0.05.)
b. Determine the p-value in (a) and interpret its meaning.
c. What assumption about the population distribution of each
bank is necessary in (a)? Is the assumption valid for these data?
d. Based on the results of (a), is it appropriate to use the pooledvariance
t test to compare the means of the two branches?