The term regression is defined as estimating the average value of one variable for the value of another variable and means “passing back.”
Galton plotted the regression line using the diameter of sweetpeas versus the diameter of parents in1877. He mentioned Regression in his article “Regression towards mediocrity in hereditary structure.”
For example, if a group of volunteers is given 250-2500mg salt per day, the regression line is used to estimate a person in the group how much will blood pressure will go down if given less than 250 mg less salt per day.