Correlation

Question 1

Date are collected as they naturally exist
No manipulation of variables

Answer 1

Observational Studies

Question 2

Subset of observational studies
Systematic investigation of relationships among two or more variables
Predict the effect of one variable on another

Answer 2

Exploratory Research

Question 3

A statistical association
Association between two variables, X and Y

Answer 3

Correlation

Question 4

The strength of the relationship
Sign implies the direction of the relationship
Closer to 1, higher strength of relationship

Answer 4

Correlation Coefficient

Question 5

Scores represent the underlying population
Scores are normally distributed
Each subject has a score for both X and Y
X and Y are independent measures
X and Y values are observed, not controlled
Relationship between X and Y is linear, not curvilinear

Answer 5

Assumptions for Correlations

Question 6

Relationship between two variables only
Only quantifies linear relationships
Does not tell us “cause and effect”
Does not account for agreement
Highly influenced by the range of observations
Average values suppress individual variation and can inflate r

Answer 6

Limitations of Correlations

Question 7

The square of the correlation coefficient (r2)
More directly interpretable

Answer 7

Coefficient of Determination