The residual variance and the proportion of explained variation are important quantities in many statistical models and model fitting procedures. They play an important role in regression diagnostics ...

We'll calculate the historical monthly variance of the S&P 500 Total Return Index over a five-year period from August 2010 through July 2015 -- that's 60 observations (5 years x 12 months).

To determine the variance in gross profit margin that these two types of adjustments create, calculate the margin for each price/cost scenario, and subtract the results.