While Galton showed that there was a correlation between fathers and sons, his two regression lines gave a different picture. The lines in the upper part of the graph revealed that if parents were taller than average, then their children would be shorter than their parents – the children’s value regresses to the mean. Conversely, the regression lines in the lower part of the graph indicated that, if the parents were shorter than average, their children would be taller than their parents, while regressing to the mean value.
