This template demonstrates regression confidence intervals. One somewhat difficult topic in teaching regression is explaining to students why confidence intervals for regression lines are hyperbolic in shape. This template allows one to visualize the process.
The user has control over the sample size, the number of samples, the amount of error variance and heteroskedasticity (non-constant variance). Adjusting the error heteroskedasticity reveals hyperbolic shapes with narrow cones on one end and fat cones on the other end. Increase the sample size to get tighter intervals.