Keyword Description
Standard deviation
Class
Function
Where Legal
Resources |
Entry Logic |
Exit Logic |
Initial Size |
Resize (Pre-Category) |
Resize (Category-Level) |
l |
l |
l |
|
|
|
Syntax
STD_POP[COLn, X, Y]
Where n is a column number X is look back number of days Y is number of days ago to begin calc (It's recommended to leave this 0)
Example
Sample code
COL2 = STD[COL1, 30, 0]
|
Statistically if you are able to calculate an STD based on the "real" population then you would use the "N" denominator. N is the degrees of freedom or total number of items in the population. It is assumed that the real population is very large, or to put it another way that you have full access to all the knowledge of the data. However in real life it is rare that one gets to apply the statistics to the real population, rather one applies it to the sample of the population. This implies a certain degree of risk that the statistic is not correct since the sample will usually be much smaller than the population. To "offset" this risk the test loses one degree of freedom and becomes (N-1). In short the vast majority of STD tests should be used with N-1. Mechanica uses N-1 as the denominator for calculating STD whereas N is used as the denominator for calculating STD_POP. |
See also: