**Here are the answers**

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A doctor wants to estimate the HDL cholesterol of all 20-29 year old females. How many subjects are needed to estimate the HDL cholesterol within 2 points with ((% confidence assuming sigma is 14.8? Suppose the doctor would be content with 90% confidence. How does the decrease in confidence affect the sample size required?

A 99% confidence level requires **364** subjects (round up to nearest whole number)

A 90% confidence level requires** 149** subjects (round up to nearest whole number)

How does the decrease in confidence affect sample size required? (check one)

a. The sample size is the same for all levels of confidence

b. The lower the confidence level the larger the sample size**c. The lower the confidence level, the smaller the sample size **

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In a survey of 2811 adults, 1452 say they have started paying bills online in the last year. Construct a 99% confidence interval for thep opulation proportion. Interpret the results.

A 99% confidence interval for the population proportion is **( 0.492, 0.541)**

Round to nearest thousandth. Round all intermediate values to nearest thousandth.

Interpret results: check one

a. the endpoints of the given confidence interval show that adults pay bills online 99% of the time

b. with 99% confidence, it can be said that the population proportion of adults who say they have started paying bills online in the last year is between endpoints of the given confidence level.

c. with 99% confidence, it can be said that the sample proportion of adults who say they have started paying bills online in the last year is between the endpoints of the given confidence interval.

**Thanks**