In statistics, we usually deal with a large amount of numerical data. In this branch, we gather, organize, manage, compute as we will as calculate the statistical data. This data may be full of noise or variation. Sometimes, it is required to know the trend of the data that in which direction it is going, increasing or decreasing etc. The technique of doing so is called the method of least squares. The term ‘least squares’ explains a more commonly-used approach in order to solve overdetermined systems of equations in approximated manner. Instead of directly solving the equations, we usually focus to on minimizing the sum of squares of the residuals. The criterion of least squares does have important statistical interpretations. In this article, we are going to go ahead as we will as learn about least squares method .