Who can see your viewing activity?
Where can we access the recording of the lecture?
Olivia Marie Silke
Is there a way to access the workshop materials?
The materials will be available after the workshop. We will be uploading them here - https://statconsulting.uci.edu/workshop-materials/
All previous workshop materials are also available on this webpage
How is posttran different from transplant?
Posttran indicates if patient already had a transplant by time t. Transplant is just an indicator if the patient ever got a transplant, so it is not of interest in our analysis
sorry why again are there more obs or records than subjects...?
Some individuals have, for example data from before and from after having the transplant, or other variables might have changed
So this is why you have multiple records per individual
Olivia Marie Silke
can you please repeat what the incidence risk is, I couldn't type my notes fast enough. Thanks!
That’s an interesting question for live answering, so we’ll answer it live.
Remember that the recording will be available, so you don’t have to take notes
What's the interpretation for median survival or incidence rate by post-transplant? It seems odd that survival post-transplant is lower than pre-transplant
is the test for trend testing the survival curves? Or just the events observed?
whats time at risk
sorry not test for trend but the log likeihood
yes this one.
Re Anton’s question, it might be helpful to think of median survival time as median follow up instead—as that time statistic doesn’t provide any information about their vital status, only the amount of time they were in the study before transplant vs after transplant. Those receiving transplants are followed for some time after and may have a better survival rate (or maybe not) than those who did not receive transplants, but that’s not reflected in the median survival time.
Kate and Anton, it also seems an artifact of how the survival estimator is defined, you have to see the graph for that.
Does the Stata documentation address the different methods for addressing ties and pros/cons of each method?
Yes, the documentation addresses that, but essentially is a trade-off between accuracy and computational efficiency
Right, so it's comparing survival between post- vs. pre-transplant follow-up time, rather than survival between persons.
Anton - That is what I was thinking as well
Yes, a patient might be in both groups.
Olivia Marie Silke
how do we address problems when the curves cross?
There are several ways to address when the PH doesn’t hold, let’s talk about this in the next break
Would you ever use the tvc option with more then one variable?
What do you mean by different functions of t?
So theta is essentially the the variance around a random intercept like in a mixed model?
Yes, essentially, it is that
In the first model there were also repeated measures. Why would you need to address the correlation between observations in the current example but not in the first example?
A good paper on Competing risk models - Introduction to the Analysis of Survival Datain the Presence of Competing RisksPeter C. Austin, PhD; Douglas S. Lee, MD, PhD; Jason P. Fine, PhD
"sttcurve" is the best way for cometing risk analysis?---Is it also possible to use "stcompet" for competing risk analysis?
sorry I mean "stcrreg" not "sttcurve"
Can you explain why a hazard would increase or decrease over time? How might a researcher know or identify that this is happening?
Very informative! Would we be able to receive the recording or slide deck?
Yes. They will be available on the Center for Statistical Consulting website here - https://statconsulting.uci.edu/workshop-materials/
Since this is parametric model do you get a LR test for the random effect as in the frailty model?
You still stset with gsem?
Gabriela Ortiz (StataCorp)
Yes, to fit a survival model with -gsem-, you would still -stset- your data, because -stset- will create that _t variable that is being used as the dependent variable.
Thank you !!