8/9/2019 Vocabulary to Remember - LinReg

1/2

Vocabulary to Remember

Responsevariable measures the outcome of a study (dependentvariable, y)

Explanatory variable attempts to explain the observed outcomes(independent variable, x)

Scatterplot shows the relationship between two variables graphically,with the explanatory variable on the x-axis and the response variable onthe y-axis

Outlier an individual value that falls outside the overall pattern of therelationship

Positiveassociation demonstrates a direct relationship

Negative association demonstrates an indirect relationship

Strength measures how close the point in a Scatterplot lie to a simpleform such as a line

Correlation measures the direction and strength of the linerrelationship between two quantitative variables (usually written as r)

Least-squares regression a method for finding a ling thatsummarizes the relationship between two variables

Regression line a straight line that describes how a response variable

y changes as an explanatory variable x changes

Least-squares regression line the line that makes the sum of thesquares of the vertical distances of the data points from the line as smallas possible

Slope the rate of change (the amount of change in when x increasesby 1)

Intercept the value of when x=0

Coefficient of determination the proportion of the totally sample

variability that is explained by the LSRL of y on x (usually written as r orR-sq)

Residual the difference between an observed value of the responsevariable and the value predicted by the regression line (observed y predicted, or y )

8/9/2019 Vocabulary to Remember - LinReg

2/2

Residual plot a Scatterplot of the regression residuals against theexplanatory variable (help us assess the fit of a regression line)

Influential outlier an observation that, when removed, wouldmarkedly change the result of the calculation (points that are outliers in

the x direction normally) Regression outlier an observation that is far from the LSRL in the y

direction

Monotonic function f(t) moves in one direction as its argument tincreases

Transformation changing nonlinear relationships between twoquantitative variables into linear relationships

Linear growth increases by a fixed amount in each equal time period

Exponential growth increases by a fixed percentage of the previoustotal

Extrapolation predicting outside your data with a regression line

Lurking variable a variable that is not among the explanatory orresponse variables in a study and yet may influence the interpretation ofrelationships among those variables

Causation the explanatory variables causes changes in the responsevariable

Confounding variables variables whose effects on a responsevariable cannot be distinguished from each other

Experiment provides the best evidence that an association is due tocausation

Two-way table organizes data about two categorical variables

Marginal distributions the distributions of row totals and columntotals presented as percents of the table total

Simpsons paradox the reversal of the direction of a comparison or

association when data from several groups are combined to form asingle group

Standard error about the LSRL the estimated standard deviation ofresponses by a sample standard deviation of the residuals (usuallywritten s, estimates an unknown )