Documentation/How Tos/Calc: DVAR function

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DVAR

Returns the bias-corrected sample variance of values in a column of a Calc 'database' table, in rows which meet specified criteria.

Syntax:

DVAR(database_table; field; criteria_table)

where

database_table is a range defining the data to be examined.

field is the column to examine. It may be a column number (1 is the first column of the database table, 2 is the second ...) or a column header (enclosed in quotation marks ””) or a cell referring to a column header.

criteria_table is a range containing criteria, which are used to select which rows of the database_table to examine.

The Database functions overview describes these parameters in detail.

DVAR returns the bias-corrected sample variance, which assumes that the chosen rows of the database_table contain a random sample of a normally distributed population. If the chosen data are the entire population, use DVARP instead. The DVAR calculation uses this formula:

where N is the number of values included and x_i are those values.

DVAR ignores any cell containing text in the field column.

Simply put, variance is a measure of how widely spread data values are. It is the square of the standard deviation (see DSTDEV, DSTDEVP). Variance is a reliable measure only if there is enough data to examine.

Example:

In this spreadsheet:

	A	B	C	D	E
1	Name	Grade	Age	Distance to School	Weight
2	Andy	3	9	150	40
3	Betty	4	10	1000	42
4	Charles	3	10	300	51
5	Daniel	5	11	1200	48
6	Eva	2	8	650	33
7	Frank	2	7	300	42
8	Greta	1	7	200	36
9	Harry	3	9	1200	44
10	Irene	2	8	1000	42
11
12
13	Name	Grade	Age	Distance to School	Weight
14		2

DVAR(A1:E10; "Weight"; A13:E14)

returns the bias-corrected sample variance of the weights of children in the second grade. This is not a useful measure, as there are so few children.

See also:

Database functions overview

DCOUNT function, DCOUNTA function, DSUM function, DPRODUCT function,

DMAX function, DMIN function, DAVERAGE function,

DSTDEV function, DSTDEVP function, DVARP function,

DGET function

VAR function

Issues

• The OOo2.3 Help implies that 0 as a field will include the entire database table. This seems to be wrong - only the variance of a single column can be found.

• Logical values TRUE and FALSE are interpreted as 1 and 0 in the calculation. This is not compatible with Excel, which ignores logical values. This will very rarely cause difficulty.