What are the options available in the proc lifetest statement?
The PROC LIFETEST statement invokes the procedure. Optionally, this statement identifies an input and an OUTSURV= data set, and specifies the computation details of the survivor function estimation. The options listed in Table 49.1 are available in the PROC LIFETEST statement and are described in alphabetic order.
What is the SAS data set used by Proc lifetest?
names the SAS data set used by PROC LIFETEST. By default, the most recently created SAS data set is used. specifies a descriptive string of up to 256 characters that appears in the "Description" field of the traditional graphics catalog. The description does not appear in the plots.
Does Proc lifetest provide one-tail or two-tail p-values?
PROC LIFETEST provides both one-tail and two-tail p-values for the test. Computational FormulasF4365 Rank Tests for the Association of Survival Time with Covariates
How are survival time tests calculated in SAS?
These tests are computed by pooling over any defined strata, thus adjusting for the stratum variables. One change in SAS 9.2 and later is that the calculation of confidence limits for the quartiles of survival time is based on the transformation specified by theCONFTYPE=option.
What does Proc Lifetest do?
The LIFETEST procedure computes nonparametric estimates of the survival distribution function. You can request either the product-limit (Kaplan and Meier) or the life-table (actuarial) estimate of the distribution. PROC LIFETEST computes nonparametric tests to compare the survival curves of two or more groups.
What are the two methods of survivor functions for which proc Lifetest produces estimates?
The LIFETEST procedure can be used to compute nonparametric estimates of the survivor function either by the product-limit method (also called the Kaplan-Meier method) or by the life table method.
What is the difference between Proc Lifetest and proc Phreg?
Re: Proc Lifetest vs Proc phreg It describes both procedures and compares them. Briefly, LIFETEST provides a nonparametric estimate of the survival times. PHREG fits a (semi)parametric Cox model. In the Cox model you get parameter estimates that you can use to interpret the strength and significane of effects.
How do you interpret survival analysis results?
The lines represent survival curves of the two groups. A vertical drop in the curves indicates an event. The vertical tick mark on the curves means that a patient was censored at this time. At time zero, the survival probability is 1.0 (or 100% of the participants are alive).
What is the purpose of the LIFETEST procedure?
You can use the LIFETEST procedure to compute nonparametric estimates of the survivor functions, to compare survival curves, and to compute rank tests for association of the failure time variable with covariates.
Does Drug X affect the survival curve?
Rats treated with Drug X live significantly longer than those treated with Placebo. Since the survival curves for the two treatments differ primarily at longer survival times, the Wilcoxon test, which places more weight on shorter survival times, becomes less significant than the log-rank test.
What is the default value for the survivor function?
For example, the option ALPHA=0.05 requests the 95% confidence limits for the survivor function. The default value is 0.05.
What is the standard error of the survivor function?
specifies that the standard error of the survivor function (SDF_STDERR) be output to the OUTSURV= data set. If the life-table method is used, the standard error of the density function (PDF_STDERR) and the standard error of the hazard function (HAZ_STDERR) are also output.
What is the default value for sweeping a covariance matrix?
The test requires that a pivot for sweeping a covariance matrix be at least this number times a norm of the matrix. The default value is 1E–12.
When to use independent samples t-test?
An independent samples t-test is used when you want to compare the means of a normally distributed interval dependent variable for two independent groups.
When is the Z test used?
It is used when population standard deviation is known. If the sample size is less than 30 then t-test is applicable.
What is trend test?
computes the trend tests for testing the null hypothesis that the population hazards rate are the same versus an ordered alternatives. If there is only one STRATA variable and the variable is numeric, the unformatted values of the variable are used as the scores; otherwise, the scores are in the given order of the strata.
Can you specify more than one variable in a strata?
More than one variable can be specified in the STRATA statement , and each numeric variable can be followed by a list. Each interval contains its lower endpoint but not its upper endpoint. The corresponding strata are formed by the combination of levels.