1, Understanding correlations

Bivariate

A study examining the relationship between two variables.

Pearson correlation coefficient (r)

A statistic from -1 to +1 measuring the direction and strength of a linear relationship.

Positive correlation

As one variable increases, the other tends to increase.

Negative correlation

As one variable increases, the other tends to decrease.

Strength of a correlation

How strong the relationship between two variables is; values closer to -1 or +1 indicate stronger correlations.

Morling’s updated ranges

Approximate guidelines: .10 = weak, .20 = moderate, .30 = strong. Check your class notes for the exact ranges.

Curvilinear relationship

A relationship between two variables that follows a curve instead of a straight line.

Restriction of range

When a sample has limited variation in a variable, potentially making a correlation appear weaker.