Unit 4 Vocabulary

Scatterplot The most popular way to display a relationship between 2 quantitative variables

Explanatory Variable Variable that we think explains or causes changes in the response variable

Response Variable A variable that measures an outcome or result of a study

Overall Pattern As in any graph of data, look for the overall pattern and for striking deviations from that pattern

To Describe the Pattern of a Scatterplot: DOFS Direction Form Strength Outliers

Correlation Describes the direction and strength of a straight line relationship between two quantitative variables. Usually written as r Memorize this formula

Positive Correlation Above average values of one tend to accompany above average values of the other Slopes upward as we move from left to right

Negative Correlation Above average values of one tend to accompany below average values of the other Scatterplot slopes downward from left to right

Correlation is ALWAYS Between -1 to 1

Regression Line Straight line that describes how a response variable y changes as an explanatory variable x changes We use this to predict y

Least Squares Regression Line Y on x is the line that makes the sum of the squares of the vertical distances of the data points from the line as small as possible

Slope The amount by which y changes when x increases by one unit

Y-Intercept Where the line intersects the Y axis

Residual Observed y – predicted y

Square of the Correlation The fraction of the variation in the values of y that is explained by the least-squares regression of y on x

Lurking Variable Variable that has an important effect on the relationship among the variables in a study but is not one of the explanatory variables studied

Common Response Refers to changes in both the explanatory and response variables that result from changes in another variable

Confounding Two variables are confounded when their effects are on a response variable cannot be distinguished from each other