MATH 124 UCLA Scatterplots & Product Moment Correlation Exam Practice

A correlation, whether product-moment or rank order, has to be between:

Select one:

a. ??$??$ and ?$?$

b. 0 and 1

c. 0 and ?$?$

d. -1 and 1

e. ??$??$ and 1

If you have two measurement variables you want to correlate and one is badly skewed, you most likely want to take:

Select one:

a. rank order correlation (Spearman’s ??$?$)

b. product-moment correlation (Pearson’s r)

c. non-linear correlation

d. you should not use any correlation measure with skewed data

e. least-squares correlation

Based on the scatterplot and statistics above, what is the nature of the correlation between eye fatigue and sleep?

Select one:

a. postive

b. zero

c. negative

If I were trying to guess someone’s sleep quality and didn’t know anything about the person, I would just guess the mean sleep quality score. After all, the mean is the “central” figure and is a good measure of what is typical. But if I know the person’s eye fatigue score, it helps me guess their sleep quality. How much does it help?

Select one:

a. It lowers random error in guessing sleep quality by 39%

b. It lowers random error in guessing sleep quality by 62%

c. It lowers random error in guessing sleep quality by 86%

d. It does not help at all; the two variables are zero correlated

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Question text

When eye fatigue increases by 1 unit, sleep quality tends to:

Select one:

a. decrease by 1 unit

b. decrease by 0.39 units

c. decrease by 0.835 units

d. increase by 1 unit

e. increase by 0.835 units

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