Chapter 8.1, Problem 19E

(a)

To determine

To Explain: the if the confidence levels were increased to 99 percent, happen to the length of the interval.

Answer to Problem 19E

Increases

Explanation of Solution

If increase the confidence level from 95% to 99% , then there are more confident that the confidence that the confidence interval is having the true population parameter and therefore the confidence interval requires to have more possible value for the true population parameter.

This then means that the confidence interval requires being wider and therefore the length of the interval increases.

(b)

To determine

To Explain: that 95 percent confidence interval on the basis of double the sample size comparing to the original 95 percent interval.

Answer to Problem 19E

Confidence interval on the basis of double the sample size is narrower than the original confidence interval.

Explanation of Solution

Doubling the sample size and therefore the sample size increases

If the sample size increases, then it contain more details about the population and therefore estimates would be more accurate.

If the estimates are more accurate, then the estimate is closer to the true value of the population parameter and therefore the confidence interval requires being narrower.

(c)

To determine

To find: that not included in the $\pm 3$ percentage point margin of error.

Explanation of Solution

The margin of error only includes possible variation and therefore is not account for the errors made during the collection of the sample date.

Other possible types of bias are:

Selection or under coverage bias would exclude part of the population.

Measurement or response bias would use a procedure that show different values from the correct value.

Non response bias is the results of not having data for everybody in the sample.