What is strata in Proc Lifetest?

What is strata in Proc Lifetest?

In the STRATA statement, the variable Treatment is specified, which indicates that the data are to be divided into strata based on the values of Treatment. PROC LIFETEST computes the product- limit estimate for each stratum and tests whether the survivor functions are identical across strata.

What is Phreg?

The PHREG procedure performs regression analysis of survival data based on the Cox proportional hazards model. Cox’s semiparametric model is widely used in the analysis of survival data to explain the effect of explanatory variables on hazard rates.

What is ODS trace?

Writes to the SAS log a record of each output object that is created, or suppresses the writing of this record.

How do you interpret hazard ratio?

It is the result of comparing the hazard function among exposed to the hazard function among non-exposed. As for the other measures of association, a hazard ratio of 1 means lack of association, a hazard ratio greater than 1 suggests an increased risk, and a hazard ratio below 1 suggests a smaller risk.

What is SAS Phreg?

Proc TPHREG is an experimental procedure that incorporates two new features into the PHREG procedure: the CLASS statement and the CONTRAST statement. PROC GLMSELECT combines features from these two procedures to create a useful new model selection tool. TPHREG. PROC PHREG is used for proportional hazard modeling in SAS …

What is Proc Phreg?

PROC PHREG is a SAS procedure that implements the Cox model and computes the hazard ratio estimate. For continuous explanatory variables, the interpretation of the hazard ratio is straightforward. The time-dependent variables and non-proportional hazards are not considered in this paper.

What is the strata statement in Proc lifetest?

The STRATA statement identifies the variables that determine the strata levels. Strata are formed according to the nonmissing values of these variables. The MISSING option can be used to allow missing values as a valid stratum level.

What is displayed in test of equality over strata?

The “Test of Equality over Strata” table is displayed if an unstratified k -sample test is carried out. The table contains the chi-square statistics, degrees of freedom, and p -values of the nonparametric tests and the likelihood ratio test (that is based on the exponential distribution).

How are the levels of a strata formed?

The corresponding strata are formed by the combination of levels. If a variable is numeric and is followed by a list, then the levels for that variable correspond to the intervals defined by the list. The initial interval is assumed to start at , and the final interval is assumed to end at .

Which is an example of a strata statement?

The specification of a STRATA variable can have any of the following forms: This statement also specifies that the Age strata be further subdivided by values of the variable Sex. In this example, there are six age groups by two sex groups, forming a total of 12 strata.