AP Stats Chapter 3 Vocab

scatter plot

a graph which shows the relationship between two quantitative variables measured on the same individual

residual plot

a scatterplot of the residuals against the explanatory variable x; helps assess how well a regression line fits the data

regression line

a straight line that describes how a response variable ychanges as an explanatory variable xchanges

y-intercept

a; the predicted value of y when x = 0

outlier

an observation that lies outside the overall pattern of the other observations

slope

b; the rate at which the predicted response (y hat) changes along the line as the explanatory variable x changes

standard deviation of the residuals

gives the approximate size of a typical or average prediction error (residual)

negative association

high values of one variable tend to occur with low values of the other variable

positive association

higher values of the two variables tend to occur together

residual

the differences between the observed and the predicted values of y; equals observed y minus predicted y

least-squares regression line

the line that makes the sum of the squared residuals as small as possible

equation of the least squares regression line

the straight line y hat = a +bx; that minimizes the sum of the squares of the vertical distances of the observed points from the line

coefficient of determination

r squared; the fraction of the variation in the values of y that is accounted for by the least-squares regression line of y and x

influential observation

individual points that substantially change the correlation or the regression line

explanatory variable

may help explain or influence changes in a response variable

variation

the average squared distance

response variable

measures an outcome of a study

correlation

measures the strength and direction of the linear association between two quantitative variables x and y