This note, the first in a series on regression analysis, introduces the simple linear model (one X-variable), together with least squares, as a procedure for estimating the coefficients in the model. The standard error of estimate, adjusted R-square, and standard error of the coefficients are all introduced and explained. The presentation of formulas is kept to a minimum, and an illustrative example is used throughout the note. This note replaces UVA-QA-0270.