Help with KM curves

[NA1234]

Hi all

A basic question but I would appreciate your collective help. I am assessing the rate of failure of a medical device, of which there are two main types. I am able to create a KM curve on SPSS showing the failure event rate for the total cohort, and can also create one showing separate curves for the two devices. I am struggling to make a plot which shows all three curves together i.e. total cohort, device 1 and device 2. Can anybody tell me how to do this please?

Thanks

 

[hlsmith]

Well this isn't usually done - that is likely why you are coming into issues. If you really wanted to do it, I would imagine you could just merge two sets of the same data together and create a categorical variable for device #1, device #2, and for one of the datasets just rename device #1 and device #2 into a new group called pooled. Then plot based on this variable - given SPSS can plot three curves, which I am assuming it can.

 

[fed2]

sas proc lifetest does this by default i believe. SPSS sux generally. https://www.sas.com/en_us/software/on-demand-for-academics.html