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 4 points with \( 99 \% \) confidence assuming \( \mathrm{s}=19.6 \) based on earlier studies? Suppose the doctor would be content with \( 95 \% \) confidence. How does the decrease in confidence affect the sample size required? E 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 \( 95 \% \) confidence level requires \( \square \) subjects. (Round up to the nearest subject.)

In how many ways can a committee of 5 students be formed from 10 students?

4 If the point \( (30,50) \) is the point of intersection of the ascending and descending curves, then the sum of its frequency equals \( \begin{array}{llll}\text { (a) } 30 & \text { (b) } 50 & \text { (c) } 60 & \text { (d) } 100\end{array} \)

Scores on a test have a mean of 78 and a standard deviation of 13 . Tom has a score of 66 . Convert Tom's score to a \( z \)-score, rounded to the nearest hundredth.

If a scatter plot shows points that are closely clustered together, what can you infer about the correlation between the variables?

a) Find the critical \( \chi^{2}- \) value for a left-tailed test when \( n=11 \) and \( \alpha=0.01 \). marks] b) Find the critical \( \chi^{2}- \) value for a two-tailed test when \( n=9 \) and \( \alpha=0.05 \). marks]