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Give an example of two variables with a strong positive correlation and explain why this is so.

Scores on a dental anxiety scale range from 0 (no anxiety) to 20 (extreme anxiety). The scores are normally distributed with a mean of 11 and a standard deviation of 4. In Exercises 49-56, find the z-score for the given score on this dental anxiety scale. 18

Give an example of two variables with a strong negative correlation and explain why this is so.

Describe a situation in which a relatively large standard deviation is desirable.

What is meant by a regression line?

Scores on a dental anxiety scale range from 0 (no anxiety) to 20 (extreme anxiety). The scores are normally distributed with a mean of 11 and a standard deviation of 4. In Exercises 49-56, find the z-score for the given score on this dental anxiety scale. 20

Scores on a dental anxiety scale range from 0 (no anxiety) to 20 (extreme anxiety). The scores are normally distributed with a mean of 11 and a standard deviation of 4. In Exercises 49-56, find the z-score for the given score on this dental anxiety scale. 12

If a set of test scores has a large range but a small standard deviation, describe what this means about students' performance on the test.

Construct a grouped frequency distribution for the following data, showing the length, in miles, of the 25 longest rivers in the United States. Use five classes that have the same width. \(\begin{array}{ccccc}2540 & 2340 & 1980 & 1900 & 1900 \\ 1460 & 1450 & 1420 & 1310 & 1290 \\ 1280 & 1240 & 1040 & 990 & 926 \\ 906 & 886 & 862 & 800 & 774 \\\ 743 & 724 & 692 & 659 & 649\end{array}\)

When all points in a scatter plot fall on the regression line, what is the value of the correlation coefficient? Describe what this means.