Describe about regression analysis

An illustration from the automobile industry is befitting for explaining the forecasting method that uses simple regression analysis. Let's presume that a statistician has data on sales of American-made automobiles in the U.S. for the last 25 years. He/she has also determined that sale of automobiles is related to the real disposable income of individuals. The statistician also has available the time series data (for the last 25 years) on real disposable income. Presume that relationship between the time series on sales of American-made automobiles and real disposable income of consumers is essentially linear and it can therefore be represented by a straight line. A rigorous mathematical method is used to locate the straight line which most accurately represents the relationship between time series on auto sales and disposable income.