7: Correlation

Question 1

What is bivariate correlation?

Answer 1

Examines relationship between two variables.

Question 2

What is a strong correlation?

Answer 2

0.9 - 0.7 (+/-)

Question 3

What is a moderate correlation?

Answer 3

0.6 - 0.4 (+/-)

Question 4

What is a weak correlation?

Answer 4

0.3 - 0.1 (+/-)

Question 5

Pearson’s r assumptions

Answer 5

Normal distribution, sensitive to outliers, and sensitive to range restrictions.

Question 6

How is covariance calculated?

Answer 6

1. For each datapoint, calculate the difference from the mean of x and from the mean of y.
2. Multiply the differences.
3. Sum them.
4. Divide by N - 1.

Question 7

What is a correlation coefficient?

Answer 7

Ratio of covariance to separate variances. Separate variances are obtained by multiplying the SD for x and y.

Question 8

What is shared variance?

Answer 8

The amount of separate variances shared, expressed by r^2.

Question 9

What is a partial correlation used for?

Answer 9

Examining the relationship between two variables whilst removing the influence of a third?

Question 10

What are correlations useful for?

Answer 10

Predictions, validity (concurrent), reliability (test-retest, inter-rater), and theory verification (predictive validity).