Regression in EXCEL r2 SSE b0 b1 SST

Prediction Watch Outs Consider only the relevant range of the explanatory variable (x) Interpolation is valid Extrapolation is not!!!

Linear Regression in Excel Method 1 When all you need is the slope and intercept of a best fit line, you can use Excel functions (SLOPE and INTERCEPT) to determine these values. You can also use RSQ to find the coefficient of determination (R2)

Example #1 Using Excel’s Functions to find the slope, intercept, and coefficient of determination

Linear Regression in Excel Method 2 Performing a linear regression in Excel is very easy. Once the data have been graphed, regression can be done very simply. Just because it is easy, does not mean that a linear regression always makes sense. Graph the data first and always inspect the “quality” of the fit.

Linear Regression in Excel Method 2 When regression is done with the trend line feature of Excel, the fitted curve is automatically added to the graph.

Linear Regression in Excel Method 2 The process of performing a linear regression for a slope and intercept requires the computation of various sums using both the independent (x) values and dependant (y) values in the data set being analyzed.

Linear Regression in Excel Method 2 You can calculate the slope b1 and intercept b0 with formula’s, but Excel will do this for you  When trying to find the best fit, always start with a linear fit (unless it is obvious that won’t work), then try exponential and polynomial fits if you think you can get a better fit.

Example #2 Using Excel’s Trendline feature find the equation for a model that fits the data

Linear Regression in Excel Method 3 There is an add-in under tools (regression) that can provide you all the details resulting from a linear regression. It is easy to use, but interpreting the results requires some understanding of regression terminology

Using Excel’s Regression Analysis Tool Example #3 Using Excel’s Regression Analysis Tool

Solving Equations You can use Excel to solve a single equation. Like most things in Excel you can do this in many different ways Graphical solution (find the roots of an equation) Trial and guess Excel features…solver and goal seek

Using Graphical means to find equation solution Example #1 Using Graphical means to find equation solution

Using Goal Seek to find equation solution Example #2 Using Goal Seek to find equation solution

Using Solver to find solutions Example #3 Using Solver to find solutions