Introduction to Linear Regression

Linear regression attempts to model the relationship between two variables by fitting a linear equation to observed data. If this observed data is from the complete population, then the regression is a population regression. For this case, the determined values of the coefficients are exactly those describing the regression model for the given population. However, if the data is only a sample, then it's called sample regression. The determined values of the regression coefficients describe a regression model that is more or less "representative" for the population is thus provides just a more or less uncertain estimate.