[From Rick Marken (950124.1255)]

Rick Marken (950124.0845) said:

The intercept of the regression equation gives an estimate of r only under

(at least) the following special circumstances:

1. The average of the predictor (d) must be 0.

2. The dependent variable, h, must be measured in units of the controlled

variable, c.

After writing this I remembered that h must not be stored in screen units

because maxx/2 is added to c before the cursor is displayed. So h is stored

0 centered. d is also stored 0 centered but, in his regressions, Bruce

coverted d to screen units by adding maxx/2 to d. The intercept of the

regression was equal to the reference value for the controlled variable (319)

because, when is d = 319 h is about 0. Since h = r - kd and k is negative,

the intercept is 319 when d is 319 to predict an h of 0. So the intercept of

the regression equation gives an estimate of the reference state of the

controlled variable when the 0 of the dependent variable (h) corresponds to

screen center and the predictor variable, d, is measured in units of the

controlled variable.

There's got to be an easier way to not make a living;-)

Best

Rick