The four parameters

Use this diagram to show the four parameters of the normal model. (These can be reduced to 3 if we assume the same spread in both groups, but leave that refinement until later.)

Use the sliders to adjust the parameters. Mention the fact that the area remains constant when the spreads change so the height varies.

The blue bands under the distributions are at µ ± 2σ so they represent about 95% of the probability. Take samples and demonstrate that about 95% of the crosses are in the bands.