Figure 17.
The chart shows the probability density p of a 1 versus the value of slope a 1. A histogram spans about negative 1.2 to positive 1.2, with the highest bars near 0. A smooth curve overlays the bars and peaks at 0, indicating a symmetric normal distribution. The central bin around 0 is highlighted, and frequencies decrease evenly towards both tails.Statistical variation of the regression parameter, (assumed reasonable range of stationary condition shown by hatched region)