ASTDEV

Description: Returns the standard deviation of the fitted model, which provides a measure of the spread of the failure times. The standard deviation is the square root of the variance.

Syntax: ASTDEV(Data_Src)

Data_Src is the source data sheet for which the standard deviation is calculated.

Remarks:

The Data_Src can be one of the following values:

If using a default data source, it must be either 1, 2, 3 or 4, as selected from the Data Source Index drop-down list.
It can take a data sheet name (e.g., "Folio1!Data 1").
It can take a variable name defined in via the Defined Names window (e.g., datasource).

The variance of the life provides a measure of the spread of the failure times and is given by:

The larger the variance, the wider the spread of the failure times.

The standard deviation is the square root of the variance:

Example:

ASTDEV("Folio1!Data 1") = 37.53284511

Note that this value will vary depending on the source data set.