Simple Linear Regression
The term linear regression implies that Y|x is linearly related to x by the population regression equation Y|x = + x where the regression coefficients and are parameters to be estimated from the sample data. Denoting their estimates by a and b, respectively, we can then estimate Y|x by y from the sample regression or the fitted regression line y = a + bx where the estimates a and b represent the y intercept and slope, respectively. The symbol y is used here to distinguish between the estimated or predicted value given by the sample regression line and an actual observed experimental value y for some value of x.
Estimating the Regression Coefficient. Given the sample {(x i, y i ); i = 1, 2, …, n}, the least squares estimates a and b of the regression coefficients and are computed from the formulas and
x y