Correlations

Question 1

3 characteristics described by a correlation coefficient?

Answer 1

Strength (consistency of relationship)
Direction (positive indicates variables move together)
Form (linear vs. nonlinear)

Question 2

What factors influence the strength of meaning of a correlation

Answer 2

restricted range

outliers

Question 3

What is the difference between r and r2?

Answer 3

r - estimate of degree of relationship between two variable
r2 - determination coefficient (overlap in variance of two variables; percentage of Y captured by X) - preferred way to describe strength, more directly interpretable

Question 4

Pearson’s r

Answer 4

linear

continuous

Question 5

spearman

Answer 5

non linear

ordinal

Question 6

point biserial

Answer 6

dichotomous/continuous

similar to independent t-test

Question 7

phi coefficient

Answer 7

two dichotomous variables

similar to chi squared

Question 8

correlation vs. covariation

Answer 8

Correlation coefficient is in standardized metric versus covariance is unstandardized and is in the units of your variable
Correlation coefficient: average of the cross-products
Covariance: unstandardized coefficient that is based on the scaling of two variables