Core Mathematics - Residual analysis - part 1
Residual analysis - part 1
Residual analysis can be carried out very effectively using an Excel
spreadsheet, as demonstrated in the following sequence.
Residual analysis is used to check the quality of fit of the regression
line. So far we have fitted a regression line to some bivariate data but
now we need to ask if the line that we fitted to our data accurately
represents the pattern of the data. Has the linear regression model
captured all the essential features of the data?
Once you have entered your X and Y values we need to fit a regression line
to the data. Excel will calculate this line using the least squares
regression method. First, highlight the X and Y data, then click on the
chart wizard in the tool bar. Follow the instructions to create a
scatterplot and insert this chart next to your data as can be seen above.
To fit a regression line to these data we need to click on one point on the
graph and then go to 'insert trendline' under the insert menu, and under
the options menu select 'show equation and r value'.
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