**MSDn** calculates the moving standard deviation of a specified variable.
__SYNTAX:__

**MSDn(Cx, ***optional **Time Increment***)**

where :

**Cx** is a conditional variable x

**n** specifies the number of days to calculate for. If daily detail variables are used returns the n "slot" moving standard deviation (ie for an hourly variable would specify the number of hours, for a 15 minute variable the number of 15 minute slots.

**Time Increment** Optional - specifies the source variables (Cx) Frequency when the Source Variable (CX) and target variable's (i.e. the variable being calculated) frequencies do not match.

__NOTES:__

The data points do not need to be on consecutive days/data slots.

Calculates every day that it can find **n** values, searching up to one year (366 days) backward

Does not calculate if **n** values are not available

Calculates the "Sample Standard Deviation" (not the population Standard Deviation), i.e. uses the formula:

Where n is the number of samples, and x bar is the mean.

**SEE ALSO: **LSDn

**EXAMPLE 1: Get the Standard Deviation of the last 7 days. **

Source variable (1) is set to Daily and Target variable (9) is also set to Daily. Because both the Source and Target variables are the same (Daily), the *time increment* BYDAY will be used.

**V9= MSD7(C1)**

Variable 9 will be the standard deviation of the last 7 days values of variable 1:

**EXAMPLE 2: Moving 4 hour Standard Deviation**

Source variable (2) is set to Hourly and Target variable (62) is also set to Hourly.

**V62= MSD4(C2)**

Variable 9 will be the standard deviation of the last 7 days values of variable 1: