Chapter 16 Quiz Review

Correlations are best suited for ____ data.

• Discrete

• Continuous

What do we call our x-axis in dealing with correlations?

• Predictor

• Criterion

• Factor

• Level

Answer explanation

The predictor variable is similar to an independent variable. You think it's the best explanation of your outcome.

Which of the following contains the strongest correlation?

• r = -.61

• r = .88

• r = -.91

• r = .34

Which of the following best describes the correlation depicted to the left?

• The graph has a weak relationship.

• The graph contains no correlation.

• The graph has a positive correlation.

• The graph has a curvilinear relationship.

A researcher obtains a correlation of r = -.41 for a sample of n = 25 individuals. What is the critical value, and what must we do with our null?

• r = .396; Fail to reject the null

• r = .388; Reject the null

• r = .337; Reject the null

• r = .381; Fail to reject the null

Answer explanation

Assuming that this is a nondirectional test with α = .05, we can see that a sample of n = 25 equates to a df of 23 (25 - 2 = 23). Now, we must use our new r-table to find the corresponding r critical value which ends up being r = .396. Since r = -.41 doesn't exceed .396, we must fail to reject the null.

As the sample size gets smaller, what happens to the magnitude of the correlation necessary for significance?

• It gets larger

• It gets smaller

• It remains unaffected

• It influences our effect size

Answer explanation

With a small sample, it is easy to get a relatively good correlation just by chance. Therefore, a small sample requires a very large correlation before you can be confident that there is a real (nonzero) relationship in the population.

Which of the following would more than likely give you a negative correlation?

• Height and weight for a group of adults

• Daily high temperature and daily energy consumption for the summer

• SAT scores and college achievement

• Daily high temperature and daily energy consumption for the winter

Answer explanation

Negative: Higher temperature tends to decrease the need for heating, making this a likely negative correlation.

The data points would be clustered more closely around a straight line for a correlation of -.80 than for a correlation of +.55.

• True

• False

Answer explanation

True. Recall, the numerical value indicates the strength of the relationship. The sign only indicates the direction.

A correlation can never be greater than +1.00.

• True

• False

How would we classify a correlation that has a value of r = .68?

• Weak

• Strong

• Moderate

• No correlation