Statistics chapter 7
Scatter plots, association, and correlation
Terms
undefined, object
copy deck
- association [ Form ]
- the form we care about most is straight, but you should certainly describe other patterns you see in scatterplots
- correlation
- is a numerical measure of the direction and strength of a linear association
- lurking variable
- a variable other than x and y that simultaneously affects both variables, accounting for correlation between the two
- outlier
- a point that does not fit the overall pattern in the scatterplot
- responsive variable
- the variable that we expect might respond to the "predictor" variable -- it is usally plotted on the y-axis
- association [ Direction ]
- a positive direction or association means that, in general, as one variable increases, so does the other. when increases in one variable generally correspond to decreases in the other, the association is negative
- what are the conditions for correlation
- 1. linearity; 2. no outliers; 3. quantitative data
- association [ Strength ]
- a scatterplot is said to show a strong association if there is little scatter around the underlying relationship
- explanatory variable
- the variable that performs the role of "predictor" -- it is usally plotted on the x-axis
- explanatory, response, x and y variables
- in a scatterplot, you must choose a role for each variable. assign to the y-axis the response variable that you hope to predict or explain; assign to the x-axis the explanatory or predictor variable that accounts for, expains, predicts, or is otherwise responsible for the y-variable
- scatterplots
- a scatterplot shows the relationship between two quantitative variables measured on the same cases