13. Assessing Relationships 1 Flashcards
correlation
- measure of relationship between variables
- whether it’s significant
correlation and causality
can’t infer causality, just that a relationship exists
What 3 ways can variables be related?
- positively
- negatively
- not related
When must you assess scatterplots?
before running a correlational analysis
covariance
assess whether or not the 2 variables covary
two types of covariance
- positive
- negative
positive covariance
as one variable deviates from the mean, the other deviates in the same direction
negative covariance
as one variable deviates from the mean, the other deviates in the opposite direction
standardized measure of covariance
correlation coefficient
most common correlation coefficient
Pearson correlation coefficient (Pearson’s r)
Pearson’s r: value must be between
-1 and 1
Pearson’s r: +1 means
positive correlation
Pearson’s r: -1 means
negative correlation
Pearson’s r: 0
no relationship
effect sizes: Pearson’s r
small: +/- .1
medium: +/- .3
large: +/- .5