SAMPLING Subcommand (BOOTSTRAP command)
The SAMPLING
subcommand is
used to specify the sampling method and any associated variables.
- If
SAMPLING
is not specified, the procedure performs simple bootstrap resampling..
SIMPLE. Simple resampling. This performs case resampling with replacement from the original dataset. This is the default.
STRATIFIED (STRATA = varlist). Stratified resampling. Specify one or more variables that define strata within the dataset. This performs case resampling with replacement from the original dataset, within the strata defined by the cross-classification of strata variables, preserving the size of each stratum. Stratified bootstrap sampling can be useful when units within strata are relatively homogeneous while units across strata are very different.
RESIDUAL (RESIDUALS=varlist | PREDICTED=varlist). Residual resampling. Specify
one or more variables containing residuals from fitting a model to
the data. The model that produced the residuals should ideally be
the same model that follows BOOTSTRAP
. A residual sample is drawn by replacing each target variable value
with that case's predicted value plus a residual sampled from the
entire original set of residuals.
Specify PREDICTED
as an alternative
to RESIDUALS
when the model residuals
are not immediately available but the predicted values are. Specify
one or more variables containing predicted values from fitting a model
to the data.
If RESIDUAL
is specified,
the TARGET
keyword is required
and the variables specified on RESIDUAL
should be the residuals (or predicted values) for, and match the
order of, the variables specified on TARGET
.
WILD (RESIDUALS=varlist | PREDICTED=varlist). Wild bootstrap resampling. Specify
one or more variables containing residuals from fitting a model to
the data. The model that produced the residuals should ideally be
the same model that follows BOOTSTRAP
. A wild sample is drawn by replacing each target variable value
with that case's predicted value plus either the case's residual or
the negative of the case's residual.
Specify PREDICTED
as an alternative
to RESIDUALS
when the model residuals
are not immediately available but the predicted values are. Specify
one or more variables containing predicted values from fitting a model
to the data.
If WILD
is specified, the TARGET
keyword is required and the variables
specified on WILD
should be the
residuals (or predicted values) for, and match the order of, the variables
specified on TARGET
.