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Chapter 7: Q. T7.2 (page 486)

The Gallup Poll has decided to increase the size of its random sample of voters from about 1500 people to about 4000 people right before an election. The poll is designed to estimate the proportion of voters who favor a new law banning smoking in public buildings. The effect of this increase is to

a. reduce the bias of the estimate.

b. increase the bias of the estimate.

c. reduce the variability of the estimate.

d. increase the variability of the estimate.

e. reduce the bias and variability of the estimate.

Short Answer

Expert verified

(c) The effect of this increase is to reduce the variability of the estimate.

Step by step solution

01

Given Information

Right before an election, the Gallup Poll decided to raise the size of its random sample of voters from 1500 to 4000 persons. The purpose of the poll is to determine the percentage of voters who support a new law prohibiting smoking in public places.

02

Explanation for correct option

Because the inaccuracies are produced by the sampling techniques, sample size has no bearing on them. When the sample size is increased, the variability is reduced since a larger sample provides more information about the population and thus better estimates.

As a result, the best solution is (c)

03

Explanation for incorrect option

a. reduce the bias of the estimate is not the answer.

b. increase the bias of the estimate is not the answer.

d. increase the variability of the estimate is not the answer.

e. reduce the bias and variability of the estimate is not the answer.

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Most popular questions from this chapter

A study of voting chose 663 registered voters at random shortly after an election. Of these, 72%said they had voted in the election. Election records show that only 56%of registered voters voted in the election. Which of the following statements is true?

a. 72%is a sample; 56%is a population.

b. 72%and 56%are both statistics.

c. 72%is a statistic and 56%is a parameter.

d. 72%is a parameter and 56%is a statistic.

e. 72%and 56%are both parameters.

According to the U.S. Census, the proportion of adults in a certain county who owned their own home was 0.71. An SRS of 100 adults in a certain section of the county found that 65 owned their home. Which one of the following represents the approximate probability of obtaining a sample of 100 adults in which 65 or fewer own their home, assuming that this section of the county has the same overall proportion of adults who own their home as does the entire county?

a. (10065)(0.71)65(0.29)3510065(0.71)65(0.29)35

b. (10065)(0.29)65(0.71)3510065(0.29)65(0.71)35

c.

P(z≤0.65-0.71(0.71)(0.29)100)Pz≤0.65-0.71(0.71)(0.29)100

d.P(z≤0.65-0.71(0.65)(0.35)100)Pz≤0.65-0.71(0.65)(0.35)100

e.P(z≤0.65-0.71(0.71)(0.29)100)Pz≤0.65-0.71(0.71)(0.29)100

Squirrels and their food supply (3.2) Animal species produce more offspring when their supply of food goes up. Some animals appear able to anticipate unusual food abundance. Red squirrels eat seeds from pinecones, a food source that sometimes has very large crops. Researchers collected data on an index of the abundance of pinecones and the average number of offspring per female over 16years.4Computer output from a least-squares 4regression on these data and a residual plot are shown here

a. Is a linear model appropriate for these data? Explain.

b. Give the equation for the least-squares regression line. Define any variables you use.

c. Interpret the values of r2and sin context.

Which one of the following would be a correct interpretation if you have a z-score of +2.0 on an exam?

a. It means that you missed two questions on the exam.

b. It means that you got twice as many questions correct as the average student.

c. It means that your grade was 2 points higher than the mean grade on this exam.

d. It means that your grade was in the upper 2% of all grades on this exam.

e. It means that your grade is 2 standard deviations above the mean for this exam.

The number of undergraduates at Johns Hopkins University is approximately 2000 , while the number at Ohio State University is approximately 60,000. At both schools, a simple random sample of about 3%of the undergraduates is taken. Each sample is used to estimate the proportion p of all students at that university who own an iPod. Suppose that, in fact, p=0.80 at both schools. Which of the following is the best conclusion?

a. We expect that the estimate from Johns Hopkins will be closer to the truth than the estimate from Ohio State because it comes from a smaller population.

b. We expect that the estimate from Johns Hopkins will be closer to the truth than the estimate from Ohio State because it is based on a smaller sample size.

c. We expect that the estimate from Ohio State will be closer to the truth than the estimate from Johns Hopkins because it comes from a larger population.

d. We expect that the estimate from Ohio State will be closer to the truth than the estimate from Johns Hopkins because it is based on a larger sample size.

e. We expect that the estimate from Johns Hopkins will be about the same distance from the truth as the estimate from Ohio State because both samples are 3 % of their populations.
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