Figure 18.

The Bar-Tip Limit (BTL) error is substantially independent of education. Mean BTL indices for each participant plotted against general education level, number of psychology courses taken, and number of statistics courses taken (each reported via the four-point scale shown on the respective graph). The black line is the least-squares regression line, computed with rated responses treated as interval-scale data. Axis ranges and graph aspect ratios were chosen by ShowMyData.org such that the physical slope of each regression line equals its respective correlation coefficient (r).