Hi
I am developing a series of Cox regression models. One observation (site_id 10434) has very high DFBETA statistics for the categorical covariate
season. I therefore want to exclude this observation from the analysis and so I type
IF (site_id = '10434') season = ''.
EXECUTE.
and then rerun the Cox regression model. Unexpectedly, this second run produced outputs (survival probability and cumulative hazard) for this record.
However, if I set a scale variable used in the model to $SYSMIS (see below), the second run does
not produce outputs – as expected.
IF (site_id = '10434') no_previous_planned_proactives_grp = $SYSMIS.
EXECUTE.
Why doesn’t setting a categorical covariate to ‘’ for a record exclude the record from the Cox regression procedure?
Thank you for your help
Atai
Dr Atai Winkler
Principal Consultant
PAM Analytics
[hidden email]
Skype: ataiwinkler
www.pamanalytics.com
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