It's awesome that he mentioned SUMPRODUCT, which is a function that anybody who uses Excel for startups should master. It allows you to do things like calculate

It's awesome that he mentioned SUMPRODUCT, which is a function that anybody who uses Excel for startups should master. It allows you to do things like calculate the amount of sales in a region, which is enormously useful to analyze data and A/B tests. For instance, say you have a spreadsheet listing every sale in 2009 along with the region it was in. Column A is the sale amount per transaction. Column B is the region its in. You could write a SUMPRODUCT formula to see how much revenue you made in the West region, like so: =SUMPRODUCT ( ( A1:A1000 ) * ( B1:B1000 = "WEST" ) ) You could repeat the formula for every region to see how sales varied by region (or whatever metric). If Column C had another metric, you could add a further filter for that too by adding a term: =SUMPRODUCT ( ( A1:A1000 ) * ( B1:B1000 = "WEST" ) * (C1:C1000 = "Male" ) ) COUNTIF is useful for its limited purpose, but SUMPRODUCT is an incredibly powerful function that I use all the time to calculate summary stats by period and other metrics.