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Chapter 8: Q.2 (page 481)

Got shoes? The class in Exercise 1 wants to estimate the variability in the number of pairs of shoes that female students have by estimating the population variance σ2.

Short Answer

Expert verified

The sample variance is s2=202.7658.

Step by step solution

01

Given Information

Data:

02

Explanation

The mean (or average) is the sum of all values divided by the number of values:

x¯=50+26+…+15+5120=30.35

nis the number of values in the data set.

n=20

The sample variance is the sum of squared deviations from the mean divided by n-1:

s2=∑(x-x¯)2n-1

(50-30.35)2+(26-30.35)2+(26-30.35)2+(31-30.35)2+(57-30.35)2

+(19-30.35)2+(24-30.35)2+(22-30.35)2+(23-30.35)2+(38-30.35)2

+(13-630.35)2+(50-30.35)2+(13-30.35)2+(34-30.35)2+(23-30.35)2

+(30-30.35)2+(49-30.35)2+(13-30.35)2+(15-30.35)2+(51-30.35)220-1

=202.7658

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Most popular questions from this chapter

In each of the following situations, discuss whether it would be appropriate to construct a one-sample tinterval to estimate the population mean.

(a) We want to estimate the average age at which U.S. presidents have died. So we obtain a list of all U.S. presidents who have died and their ages at death.

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(a) Construct and interpret a 95%confidence interval for the mean difference μin the zinc concentrations from these two locations in the wells.

(b) Does your interval in part (a) give convincing evidence of a difference in zinc concentrations at the top and bottom of wells in the region? Justify your answer.

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(b) 90% confidence; n=50.

(c) 95% confidence; n=25.

(d) 95%confidence; n=50.

(e) n=100 at any confidence level.

Many television viewers express doubts about the validity of certain commercials. In an attempt to answer their critics, Timex Group USA wishes to estimate the proportion of consumers who believe what is shown in Timex television commercials. Let prepresent the true proportion of consumers who believe what is shown in Timex television commercials. What is the smallest number of consumers that Timex can survey to guarantee a margin of error of 0.05or less at a 99%confidence level?

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Scientists collect data on the blood cholesterol levels (milligrams per deciliter of blood) of a random sample of 24laboratory rats. A 95%confidence interval for the mean blood cholesterol level Mis 80.2to 89.8. Which of the following would cause the most worry about the validity of this interval?

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