Week 6: Association Between Two Variables

Question 1

association

Answer 1

variables covary

Question 2

dependence

Answer 2

one variable causes (determines) the other variable

independent variable determines dependent variable

Question 3

causation

Answer 3

X cause Y and X is associated with Y

Question 4

common response

Answer 4

Z cause X and Y, and X and Y have association

Question 5

confounding

Answer 5

Z cause Y and X is associated with Y and Z

Question 6

association and dependence

Answer 6

association does not imply dependence, but dependence does imply association

Question 7

Covariance formula

Answer 7

see slides

Question 8

formula for Pearson’s R

Answer 8

see slides

Question 9

estimating Pearson’s R from scatterplots

Answer 9

see slides

Question 10

Rules of thumb for interpreting magnitude of r

Answer 10

• 0.1, small
• 0.3, medium
• 0.5, large

Question 11

caveats to interpretation of Pearson’s r

Answer 11

• non-linear relationships
• outliers
• heterogeneity
• restriction of range