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0answers
10 views

Perform logrank test only with survival probabilities

So I have survival probabilities for 2 groups at years 1, 3, 5, 10,15. Is there way to detect significant differnece between all of them as a whole or even between each pair? I don't have the ...
1
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2answers
47 views

Log-rank / Cox analysis with very unequal sized groups: alternative calculations of p-value?

I would like to set up a series of tests on the difference in survival between two very unequal sized groups. Generally either log-rank (using the R survdiff function) or a cox regression (R coxph) ...
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1answer
56 views

log-rank test in R

I need to use the survdiff function to statistically compare (using log-rank test) the following survival functions: (1) Male (Sex=1) and Female (Sex=2) (2) ...
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1answer
39 views

Logrank test for trend (proportional hazards)

How one can create a logrank test for trend and does it differ from normal logrank test? Any suggestions or literature? Maybe some R examples and functions?
2
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1answer
40 views

Validity of Log-rank p-value when there are zero events in one group?

I am looking to do a Kaplan Meier analysis to look at survival in two groups. I have 21 people in group A and 17 people in group B. 5 people in group B died at various times, 0 people in group A died, ...
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0answers
278 views

Sample size / power calculation for logrank survival test

I have really little idea of survival analysis. I am aware that logrank is a special case of Cox' proportional hazards model, and that tons of R packages and scripts address the problem of power / ...
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0answers
49 views

Error in books formula concerning the log-rank test?

I am currently reading the following book: Clinical Trials: A Practical Guide to Design, Analysis, and Reporting by Duolao Wang, Ameet Bakhai (2006) On page 243-244 there is an example about the ...
3
votes
1answer
232 views

In which situation does the log-rank test have low power?

This question is complementary to question 1 asked by @Jesse here. It is about the case when we don't find a significant result when performing the log-rank test and when the proportional hazard ...
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0answers
155 views

KM curve: log rank test significant but HR crosses 1

Hello and thanks for this source about statistics. My Problem is about a situation where Kaplan Meier curves differ in meaning of a significant log rank test, but the hazard ratio crosses 1 when ...
1
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2answers
134 views

Combining several survival experiments

In four independent experiments, two strains (A and B) were compared in their respective survival curves. Two experiments show a clear-cut result (A survives at 100%, almost half B dies). Two further ...
3
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1answer
2k views

Difference between survdiff log-rank and coxph log-rank

I'm using the survival package in R to analyze clinical data. I am analyzing two different groups of patients, when I calculate survdiff in order to compare the curves, I got p= 0.135, but when I ...
3
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0answers
282 views

How do I compare 2 models?

I would like to show that a new biomarker (let's say percent tumor volume reduction at 3 weeks of treatment estimated with automatic methods) performs better than an old one (same measure, but based ...
5
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3answers
981 views

How best to analyze length of stay data in a hospital-based RCT?

I am interested in knowing whether or not there is a consensus about the optimal way to analyze hospital length of stay (LOS) data from a RCT. This is typically a very right-skewed distribution, ...
5
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2answers
874 views

Which algorithm to compute p-value of logrank test with three or more groups is best?

There seem to be two different algorithms for comparing three or more survival curves using the logrank test. Algorithm A. Found in books by Altman and Machin. Computed by GraphPad Prism. This ...
5
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1answer
2k views

How should I deal with the consequences of proportional hazards violations in log-rank (and related) tests?

I have (censored) time-to event data for subjects in four groups. I would like to do something like a logrank test, but the survival curves do not satisfy the proportional hazards assumption. I ...
2
votes
1answer
202 views

Is there a repeated measures aware version of the logrank test?

I am looking for a repeated measures version of the Logrank test. If I am correct, I am looking for an equivalent of the Friedman test for survival data. Any suggestions on where to look? (and R ...