Week 5 Correlation Flashcards
What is the correlation coefficient?
A number that indicates the extent to which two variables are related.
What is the scale of correlation coefficient values?
-1.0 to 1.0
What does it mean if the correlation coefficient is 1.0?
Perfect positive linear relationship
What does it mean if the correlation coefficient is 0.5?
Positive linear relationship
What does it mean if the correlation coefficient is 0?
No linear relationship between the variables
What does it mean if the correlation coefficient is -1.0?
Perfect negative linear relationship
What does it mean if the correlation coefficient is -0.5?
Negative linear relationship
What are the assuptions to be tested before carrying out Pearson’s correlation analyses?
- Normal distribution
- Homogeneity of variance
- Interval/ratio
- Independence
- Linear relationship
What does homegeneity of variance mean?
Variance of one variable is stable at all levels of the other variable (most value fit within two parallel lines)
What do we find out if we square the Pearson coefficient?
The variance explained due to the variable
What can we not assume about correlations?
Correlation does not mean causation
Correlation does not necessarily mean agreement
What does a two tailed Pearson’s correlation do?
The test half’s the p value and tests for a relationship in both tails
What do a one-tailed Pearson’s correlation do?
The test uses the whole p-value and tests for a relationship in one tail
What type of hypothesis would you use a two tailed Pearson’s correlation?
Non-directional alternative hypothesis
What type of hypothesis would you use a one tailed Pearson’s correlation?
Directional alternative hypothesis
