23 terms

Response Variable

measures an outcome of a study

Explanatory Variable

may help explain or predict changes in a response variable

Scatterplot

shows the relationship between two quantitative variables measured on the same individuals

Positive Association

data points that generally go upward from left to right, somewhat linear

Negative Association

data points that generally go downward from left to right, somewhat linear

Strength

determined by how closely the points follow a clear form

Outlier

an individual value that falls outside the overall pattern of the relationship

Correlation

measures the direction and strength of the linear relationship between two quantitative variables

Regression Line

a line that describes how a response variable y changes as an explanatory variable x changes

Extrapolation

the use of a regression line for prediction outside the range of values of the explanatory variable x used to obtain the line

Least-Squares Regression Line (LSRL)

the line that makes the sum of the squared vertical distances of the data points from the line as small as possible (best-fit line on a scatter plot)

Residual

the difference between an observed value of the response variable and the value predicted by the regression line (a.k.a. prediction error)

Residual Plot

a scatterplot of the regression residuals plotted against the explanatory variable

Coefficient of Determination

the portion (%) of the variation in the response variable (y) that is explained by the least-squares regression line of y and x

Lurking (Confounding) Variable

a variable that is not among the explanatory or response variables in a study and yet may influence the interpretation of relationships among those variables

Residual (formula)

Least squares regression line (formula)

coefficient of determination (symbol)

correlation coefficient (symbol)

predicted value (symbol)

D.O.F.S.

direction, outliers, form, strength - all things that should be addressed when describing the relationship between two quantitative variables

standard deviation of the residuals

the approximate size of a typical prediction error (residual) when we use the least squares regression line to predict the value of a specific response variable

standard deviation of the residuals (symbol)

s