Correlation, Causation, Moderation, Meditation

What does r = 0.00 indicate?

No linear relationship OR a curvilinear relationship (ex. quadratic)

T/F: r = .80 is twice as large as r = .40

False; r is NOT on a ratio scale

Coefficient of Determination (r²)

Proportion of variance in one variable accounted for by the other variable - this is on a ratio scale! 

What tells us about systematic variance?

r²

What is statistical significance affected by?

• Sample Size

• Correlation magnitude

More participants means you are (more/less) likely to find a statistically significant result

More

A smaller correlation means you are (more/less) likely to find a statistically significant result. 

Less 

3 Criteria for Inferring Causality

• Covariation

• Order in Time

• Removal of all other variables

Covariation

Changes in one variable are associated with changes in the other variable

Covariation

Changes in one variable are associated with changes in the other variable

Order in Time 

The presumed causal variable must occur before the other variable 

Removal of all other variables

All other variables that may affect the relationship between the two variables are controlled or eliminated

Spurious Correlation

Correlation between two variables due to their relation to other variables

Which criteria for causation is satisfied by a correlation?

Covariance 

Moderation

When one variables changes the effect of another variable on an outcome (the same thing as an interaction!)

Which is the same as an interaction: moderation or mediation?

Moderation

What types of variables can moderating variables be?

Grouping variables or continuous variables 

____ is about “when.”

Moderation

____ is about “how.”

Mediation

What does the mediating variable explain? 

How we get from one variable to another; mediating variable M is situated between X and Y (like links on a chain)

With a mediator, does the relationship between X and Y change with different levels of M?

No

With a moderator, does the relationship between X and Y change with different levels of M?

Yes