Statistical Formulas

Average cells	Number - Average
Average cells after subtraction	Number - Average
Average cells ignoring duplicates	Number - Average
Average cells ignoring zeros	Number - Average
Average cells in a table when a column meets multiple conditions	Number - Average
Average cells including blank cells	Number - Average
Average cells that are not errors	Number - Average
Average cells that are not hidden	Number - Average
Average cells using the n largest numbers	Number - Average
Average cells using the n last numbers	Number - Average
Average cells using the n smallest numbers	Number - Average
Average cells using weighted average	Number - Average

Average cells Number - Average
Average cells after subtraction Number - Average
Average cells ignoring duplicates Number - Average
Average cells ignoring zeros Number - Average
Average cells in a table when a column meets multiple conditions Number - Average
Average cells including blank cells Number - Average
Average cells that are not errors Number - Average
Average cells that are not hidden Number - Average
Average cells using the n largest numbers Number - Average
Average cells using the n last numbers Number - Average
Average cells using the n smallest numbers Number - Average
Average cells using weighted average Number - Average

Average cells after subtraction

Lets suppose that we are keeping a record of the amount we spend every day.

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1	copy from image

The formulas in column "E" calculate the difference between the amount earned and the amount spent.
The formula in cell "E3" is just "=D3-C3" and then copied down to cell "E13" and the formula in cell "E15" calculates the average from these values.
You can remove the whole of column "E" from the calculation by using an array formula. This combines calculating the difference and the average all in a single formula.
The formula in cell "E16" first calculates the difference and then returns an array of differences to the AVERAGE function.

Average cells including blank cells

The AVERAGE and AVERAGEA functions will always exclude blank cells

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1	??

'=SUM(D2:D5)/ROWS(D2:D5)
'=SUM(D2:D5)/(COUNT(D2:D5)+COUNTBLANK(D2:D5))

Average cells ignoring duplicates

If you want to average three numbers, but if two are the same only average two of the numbers you could use the following where Rge is a three cell range.

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1	"=AVERAGE(IF(SUM(COUNTIF(Rge,Rge)) = 3,Rge,IF(COUNTIF(Rge,Rge)>1.Rge,""))).

This formula counts the number of cells in the discontinuous range that contains a value greater than 20 "=INDEX(FREQUENCY((A1,A3,A5),20),2)".

Average cells ignoring zeros

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1	{=AVERAGE(IF(CellRange<>0,CellRange))}

Average cells using the n largest numbers

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1	AVERAGE( LARGE( B2:D5, {1,2,3} )

AVERAGE
LARGE

Average cells using the n smallest numbers

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1	AVERAGE( SMALL( B2:D5, {1,2,3} )

AVERAGE
SMALL