How many college students are needed to estimate the mean grade point average of all current college students in the United Sates within 20\% percentage points with a \( 99 \% \) confidence. An earlier study gave an estimate of 0.79 for the population standard deviation. \( \mathrm{n}= \)

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.

The grades on the second statistics test for Mrs. Sweeney's class are in the following list. Find the frequency distribution for the grades, \[ \text { D, F, B, D, A, F, F, B, F, F, B, C, C, C, B, F, C, A, B, B, F } \]

Determine the point estimate of the population mean and margin of error for the confidence interval. Lower bound is 21 , upper bound is 29 . The point estimate of the population mean is 1

Determine whether the following statement is true or false. To construct a confidence interval about the mean, the population from which the sample is drawn must be approximately normal. This statement is

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) \( \begin{array}{l}\text { (a) Obtain a point estimate for the population proportion of adults in the country aged } 18 \text { and older who have donated blood in the past two years. } \\ \text { (Round to three decimal places as needed.) }\end{array} \)