STAT-S 300 Lecture 5: 3.1 Notes (Sep. 15)
Document Summary
Explanatory and response variables: explanatory variable- may help explain or influence changes in response variable, response variable- measures an outcome of a study. Displaying relationships: scatterplots: scatterplot- shows relationship between 2 quantitative variables measured on the same individuals (only way to display 2 quant. variables) Each individual appears as point on graph. Axes do not have to start at 0 or have same scale. Scale on each axis must be consistent and labeled: how to make a scatterplot. Decide which variable should go on each axis (if there is no explanatory- response distinction, either can go on the horizontal axis) Interpreting scatterplots: look for overall pattern and striking departures from pattern. Strength- strong, moderately strong, moderately weak, weak. Measuring linear association: correlation: correlation (r)- numerical summary of linear association. 1 < r < 1 r > 0- positive association r < 0- negative association r = 1 or r = -1- scatterplot is perfectly linear and strength = very strong.
