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help for ^stselpre^ [ec] Feb 10, 2010
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Fits proportional hazards model to case-cohort data
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^stselpre^ varlist [^if^ exp] [^in^ range] [^, nohr^ ^l^evel^(^#^)^ ^self^
{^bre^slow | ^efr^on | ^exactm^ | ^exactp^} ^nosh^ow ^force^ ]
^stselpre^ is for use with survival-time data; see help @st@. Before using the command,
data must be prepared for case-cohort analysis by ^stcascoh^; see help @stcascoh@.
Description
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^stselpre^ returns estimates and standard errors from proportional hazards fit to
case-cohort data. Coefficients are estimated according to two methods:
- Self-Prentice scheme. Risk sets uses just the sub-cohort member at risk,
- Prentice scheme. Risk sets are augmented by non sub-cohort cases when they fail.
The asymptotic Self-Prentice method variance-covariance matrix and standard errors are
computed using the simplification described in Therneau and Li (1999).
The syntax of @predict@ following ^stselpre^ is as in ^stcox^
Options
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^nohr^ specifies that coefficients rather than hazard ratios are to be displayed
^nohr^ may be typed at estimation or when replaying previously estimated results.
^level(^#^)^ specifies the confidence level for the confidence intervals of the
coefficients; see help @level@. ^level^ may be also specified when replaying previously
estimated results.
^self^ specifies that Self-Prentice method coefficient vector is to be saved in e(b).
Prentice method coefficients are saved by default.
^breslow^, ^efron^, ^exactm^, and ^exactp^ each specify a method for handling tied
deaths that the underlying ^stcox^ command executes. ^efron^ is the default.
^noshow^ prevents ^stselpre^ from displaying the identities of the key st variables
above its output.
^force^ prevents ^stselpre^ from doing some check on the data set previously prepared by ^stcascoh^.
Examples
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. ^stselpre stage age^
. ^xi: stselpre i.stage*i.histol, nohr self^
Also see
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Manual: ^[R] stcox [R] sttocc^
On-line: help for @stcascoh@ @stcox@ @sttocc@
Reference
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Therneau M T, Li H: Computing the Cox Model for Case Cohort Designs.
Lifetime Data Analysis 1999; 5: 99-112.
Author
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Enzo Coviello
Epidemiology Unit ASL BT
Italy
enzo.coviello@@alice.it