Excel 2010 changes function names like STDEV and VAR partly for Microsoft’s own benefit.
Excel 2010 has revamped all the Standard Deviation STDEV and VAR functions with the old version ‘deprecated’ or demoted.
There is now STDEV.S and STDEV.P for the sample and population versions of the function.
STDEV and STDEVP are still available for compatibility with Excel 2007 and previous version of Excel so there’s no need to rewrite your worksheets. However you will need to be careful using the new form functions in any worksheet that might be opened in an earlier version of Excel.
Similarly the VAR and VARP functions are retained for compatibility with new names VAR.S and VAR.P apparently preferred.
There is apparently NO difference in the functions themselves – only the naming has changed.
STDEVA, STDEVPA, VARA and VARPA are unchanged from earlier versions of Excel. They also calculate standard deviation but include logical values and text. Text and FALSE logicals have the value zero while TRUE equals 1.
Why the name change for STDEV.S and STDEV.P with the addition of the dot? It’s part of a new Microsoft initiative to make Excel function naming more consistent. In a complex worksheet it easy to mistake STDEV and STDEVP so adding the dot might help readability.
But if Redmond was truly interested in consistency why are the ‘A’ versions of the same functions unchanged? Surely we should now have STDEVA.S and STDEVA.P or even STDEV.A.S and STDEV.A.P ?
The new form functions are given prominence as you type with the old versions at the bottom with a warning icon against them.
This makes it easier for the unwary to choose the new name and lose the broader compatibility.
The Corporate Agenda
Another benefit to Microsoft (not users) is to make Excel worksheets less compatible with rival products. It might not have been the prime reason for the change but it certainly helps Microsoft that two common statistical functions now have names that OpenOffice and Google Docs don’t recognize?
And it’s another little encouragement for people to buy Excel 2010 too.