Correlation Coefficient Flashcards
(12 cards)
What does the correlation coefficient do?
Measures how strongly two variables are related and in what direction they are related.
What is correlation coefficient denoted as?
r
What values can r take?
Any value between -1 and +1.
What does an r value of +1 mean?
+1 = a perfectly positive correlation (when one goes up the other one always goes up)
points lie exactly on the straight line
What does an r value of -1 mean?
-1 = a perfectly negative correlation (when one goes up the other one always goes down)
points lie exactly on the straight line
What does a value of r>0 mean?
A positive slope
The closer the number to 1 the stronger the relationship
What does a value of r<0 mean?
A negative slope
The closer the number to -1 the stronger the relationship
What does r=0 mean?
There is no linear relationship between the variables.
When is correlation coefficient unsuitable?
Relationship is non-linear
Variables measured over more than 1 distinct group
One or more outliers with strong influence
Restricted sampling of individuals
How do you calculate r?
r = covariance of X and Y divided by (SD of X) x (SD of Y)
What does it mean if odds ratio = 0<or<1?
The outcome is less likely to happen in exposed subjects.
What does it mean if odds ratio = >1?
The outcome is more likely to happen in exposed subjects.
