topic Re: Proc Lifetest - Number at Risk Vs Number Left in Statistical Procedures

Proc Lifetest - Number at Risk Vs Number Left

djrisks — Wed, 12 Nov 2014 15:41:42 GMT

Hello,

Do you know why the atrisk numbers are different on a survival curve compared to the atrisk numbers that are in the ods ProductLimitEstimates dataset in the NumberAtRisk column? It seems like the atrisk numbers on the survival curve correspond to the Left column (Number Left) in the ods ProductLimitEstimates dataset? Can you help please?

Many thanks,

Kriss Harris

Re: Proc Lifetest - Number at Risk Vs Number Left

Reeza — Wed, 12 Nov 2014 15:55:25 GMT

Can you post some sample data with this issue?

Re: Proc Lifetest - Number at Risk Vs Number Left

djrisks — Wed, 12 Nov 2014 15:57:45 GMT

Okay, I will create some. Thanks.

Re: Proc Lifetest - Number at Risk Vs Number Left

djrisks — Wed, 12 Nov 2014 16:10:19 GMT

Hi Reeza,

Here is the sample code:

ods output ProductLimitEstimates = out.surv;

proc lifetest data=sashelp.BMT plots=survival(atrisk=0 to 2500 by 500) atrisk timelist = 0 to 2500 by 500;

time T * Status(0);

strata Group / test=logrank adjust=sidak;

run;

I can't attach the dataset at the moment, but you will see what I mean when you run the program and compare the Left Column with the NumberAtRisk column and then also compare them to the graph.

Thanks.

Re: Proc Lifetest - Number at Risk Vs Number Left

Reeza — Wed, 12 Nov 2014 17:42:31 GMT

For the code I ran, number at risk=number left because there are no ties or multiple occurrences with censors at the same time in this data.

The number left = number at risk seems to make sense intuitively to me except possibly when a censored and event occur at the same time?

Re: Proc Lifetest - Number at Risk Vs Number Left

djrisks — Wed, 12 Nov 2014 17:46:27 GMT

Okay thank you. Do you know which Atrisk values we should be using please when there are differences between number at risk and number left?

Re: Proc Lifetest - Number at Risk Vs Number Left

Reeza — Wed, 12 Nov 2014 17:47:17 GMT

You can generate the source code for the graph and see it references the ATRISK, check the log...

ods trace on;

ods output ProductLimitEstimates = surv;

proc lifetest data=sashelp.BMT plots=survival(atrisk=0 to 2500 by 500) atrisk timelist = 0 to 2500 by 500;

time T * Status(0);

strata Group / test=logrank adjust=sidak;

run;

ods trace off;

proc template;

source Stat.Lifetest.Graphics.ProductLimitSurvival;

run;quit;

Re: Proc Lifetest - Number at Risk Vs Number Left

djrisks — Wed, 12 Nov 2014 18:12:46 GMT

Thank you for this Reeza, I'll check.

Re: Proc Lifetest - Number at Risk Vs Number Left

djrisks — Wed, 28 Jan 2015 14:28:11 GMT

Hi Reeza,

Thank you for helping out with this. I've just gone back to it, and I can see that the template does reference the ATRISK number. I wonder why the plot uses the Left column then?

Re: Proc Lifetest - Number at Risk Vs Number Left

djrisks — Tue, 12 May 2015 16:04:47 GMT

From reading Jack Shostak's book, I've seen that a solution to the question mentioned above is to output the "survivalplot" dataset.