Correlation

Question 1

1. Measures the strength of association (linear relationship) between 2 variables
2. Used in conjunction with scatterplots

Answer 1

Correlation

Question 2

value of the correlation coefficient

Answer 2

a. –1 indicates a very strong negative correlation
b. +1 indicates a very strong positive correlation
c. As the r goes towards 0, the relationship becomes weaker.
c. 0 indicates no correlation

Question 3

the variables move in the same direction. As 1 variable ↑, the other also ↑

Answer 3

Positive Correlation

Question 4

the variables move in inverse direction. As 1 variable ↑ the other ↓

Answer 4

Negative Correlation

Question 5

The most widely used correlation statistic

Answer 5

Pearson r correlation

Question 6

Assumptions for Pearson r

Answer 6

a. Normally distributed (assumes a normal curve or bell shape for both variables)
b. Linear (assumes a straight-line relationship between each of the two continuous variables)
c. Homoscedastic (assumes that data is equally distributed about the regression line)

Question 7

1. A non-parametric test that measures the strength of dependence between 2 variables
2. Used to measure the ordinal association between 2 measured quantities.

Answer 7

Kendall rank correlation:

Question 8

A non-parametric test that is used to measure the degree of association between two variables.

Answer 8

Spearman rank correlation

Question 9

Assumption for Spearman rank

Answer 9

a. Does not carry any assumptions about the distribution of the data
b. The variables are at least ordinal and the scores must be related