W6 Correlation

Scatterplot

A graph that displays the relationship between two quantitative variables using points on a Cartesian plane

Correlation

A statistical measure that describes the degree and direction of a relationship between two variables

Linear association

A relationship between two variables that can be represented with a straight line

Non-linear association

A relationship between two variables that does not form a straight line and may be curved or more complex

Pearson’s correlation (r)

A statistic that measures the strength and direction of a linear relationship between two variables

Covariance

A value that indicates the degree to which two variables vary together

Coefficient of determination

The proportion of variance in one variable that is predictable from another variable, often expressed as r²

Correlation coefficient

A numerical value that indicates both the direction and strength of a relationship between two variables

Outlier

A data point that is distant from other observations and may affect statistical analyses

Line of best fit

A straight line that best represents the data on a scatterplot, minimizing the distance between the line and all data points

Regression

A statistical method used to predict the value of one variable based on the value of another variable

Perfect correlation

A correlation in which all data points lie exactly on a straight line, giving a correlation coefficient of 1 or -1

Regression line

The line that best predicts the criterion variable from the predictor variable in a regression analysis

Predictor variable

The independent variable used to predict outcomes in regression analysis

Criterion variable

The dependent variable being predicted in regression analysis

Deviation products

The product of the deviations of two variables from their respective means, used in calculating covariance and correlation

Range restriction

Where part of a scatterplot has different correlations than another part.

Heterogeneous samples

Samples that are diverse or varied in characteristics that can give different correlations (eg males and females)