A doctor wants to estimate the mean HDL cholesterol of all 20 - to 29 -year-old females. How many subjects are needed to estimate the mean HDL cholesterol within 3 points with \( 99 \% \) confidence assuming \( \mathrm{s}=12.9 \) based on earlier studies? Suppose the doctor would be content with \( 90 \% \) confidence. How does the decrease in confidence affect the sample size required? Click the icon to view a partial table of critical values. A \( 99 \% \) confidence level requires \( \square \) subjects. (Round up to the nearest subject.) A \( 90 \% \) confidence level requires \( \square \) subjects. (Round up to the nearest subject.) How does the decrease in confidence affect the sample size required? B. Decreasing the confidence level decreases the sample size needed. B. Decreasing the confidence level increases the sample size needed.

Homework Determine the point estimate of the population proportion, the margin of error for the following confidence interval, and the number of individuals in the sample with the specified characteristic, \( x \), for the sample size provided. Lower bound \( =0.529 \), upper bound \( =0.831, n=1500 \) (Round to the nearest thousandth as needed.) The margin of error is \( \square \). (Round to the nearest thousandth as needed.)

What is a scatter plot?

At a festival, one game involves guessing the number of candies in a plastic jar. The following data represents the guesses that people made during one hour at the festival. Complete the frequency table for this data. \[ 1382,1211,1354,1171,1058,1472,1132,1090,1132,1443,1163,1274,1112,1266,1254,1174 \]

A survey of 2283 adults in a certain large country aged 18 and older conducted by a reputable polling organization found that 406 have donated blood in the past two years. Complete parts (a) through (c) below. Click here to view the standard normal distribution table (page 1). Click here to view the standard normal distribution table (page 2) \( \begin{array}{l}\text { (a) Obtain a point estimate for the population proportion of adults in the country aged } 18 \text { and older who have donated blood in the past two years. } \\ \text { (Round to three decimal places as needed.) }\end{array} \)

Ork Explain why the \( t \)-distribution has less spread as the number of degrees of freedom increases. Choose the correct answer below. A. The \( t \)-distribution has less spread as the degrees of freedom increase because, as \( n \) increases, 2 of 8 posints information is known about \( \sigma, 9.2 .49 \) by the law of large numbers. B. The \( t \)-distribution has less spread as the degrees of freedom increase because, as \( n \) increases, s becomes closer to \( \sigma \) by the law of large numbers. C. The \( t \)-distribution has less spread as the degrees of freedom increase because, for large values of \( n \), \( n \geq 30 \), the \( t \)-distribution and the normal distribution are the sam D. The \( t \)-distribution has less spread as the degrees of freedom increase because the variability introduced into the \( t \)-statistic becomes greater as \( n \) increases.