Linear regression in Excel with Analysis ToolPak.It will give you an answer to this and many more questions: Which factors matter and which can be ignored? How closely are these factors related to each other? And how certain can you be about the predictions? But how do you know which ones are really important? Run regression analysis in Excel. You have discovered dozens, perhaps even hundreds, of factors that can possibly affect the numbers. Imagine this: you are provided with a whole lot of different data and are asked to predict next year's sales numbers for your company. The tutorial explains the basics of regression analysis and shows a few different ways to do linear regression in Excel.