# Questions tagged [logrank]

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44 questions
0answers
18 views

### Why is likelihood ratio test preferred over log rank and Wald in Cox model for small sample sizes?

It looks like a common consensus that likelihood ratio (LR) test is preferred over log rank and Wald in Cox model when sample size is small. I did some research and couldn't find any clear answer. My ...
0answers
24 views

### Why are Logrank, Wald and likelihood ratio test asymptotically equivalent?

I am trying survival analysis and it seems like a common consensus that Logrank, Wald and likelihood ratio are asymptotically equivalent I don't understand why they are asymptotically equivalent. As ...
1answer
58 views

### How to calculate log-rank test statistic

Depending on which statistics text you read you will get 2 different formulations of the log-rank test statistic. In some texts you will see it specified as: $$\frac{(O-E)^2}{E}$$ Example 1 Whilst ...
2answers
32 views

### How to properly do a Survival analysis - Question about start times

I have a monthly report that lists transactional errors made by facilities all over the country. Each row is a single error and the columns represent descriptive information about each error (ID, ...
0answers
24 views

### Can logrank test be used in non-survival data?

I recently came across with a paper, in which logrank test was used to compare hospital cost between groups. I assume the "event" variable here would be the discharge, which is 1 for everyone, and the ...
0answers
9 views

### % variation on 1/x function

My data (X) is the rank position of units sales (y). Eg. x=1 top seller, x=1000 is the 1000th top seller I know that sales number can be estimated by: units(x) = $N_0x^{(-0.5)}$ Now I would ...
0answers
50 views

### How can we analyze a dataset with a pseudoreplication problem?

I am trying to analyse a data set with a pseudoreplication problem and would be grateful if someone could give me some guidelines on the best way to deal with it. We have a set of subjects exposed to ...
1answer
26 views

### How should I decide which test to use to look for differences in Kaplan-Meier curves?

I'm conducting a survival analysis for my dissertation and have run into a bit of a road block about which test to use to look for differences in Kaplan-Meier curves between treatments. A previous ...
1answer
333 views

### R calculate log-rank p-value of survival curve at specific time [closed]

I am using survfit object from package survminer to draw a survival curve in ggplot. Now I am trying to understand how I can use ...
1answer
1k views

### Logrank p-value for >2 groups

I'm reviewing a paper that includes some survival plots for patients stratified to 3 groups (low, intermediate and high value of certain parameter), with p-value given for each plot. My understanding ...
0answers
35 views

### Cox Regression Model for toxicity

I'm trying to evaluate the toxicity of a certain treatment over time. I have 2 independent groups and I apply a treatment to one, and nothing to the second one. I thought about using logistic ...
0answers
130 views

### Survival Analysis: Significance in LogRank but not in Cox Regression

Currently, I am trying to extract the HR and 95% CI from a kaplan meier curve (used DigitizeIt plus the spreadsheet provided by Tierney et al) [Tierney JF, Stewart LA, Ghersi D, Burdett S, Sydes MR....
1answer
66 views

### How to deal with different likelihood of censoring across groups in survival analysis?

I am analysing survival data for nematode worms fed on four different bacterial diets (four groups). Each group has at least 70 events (deaths), but there is often a very uneven proportion of ...
1answer
84 views

### sample size calculation for one-sample log rank test with interims (ie group sequential)

I wonder if there is any advice for performing a sample size calculation for survival data using the one-sample log rank test with interims (ie group sequential) - ie with O'Brien-Fleming or some ...
0answers
63 views

### Is Univariate comparison of 10 subjects using log rank test in Kaplan Meier survival is statistically sound?

I have 10 subjects and want to analyse the predictors of overall survival and progression free survival using log rank test . Will conducting log rank test on such a small sample size will be ...
0answers
53 views

### A strange finding with the logrank test statistics

When I try to confirm the type I error rate of the logrank test by simulation, I found something strange... Firstly, I generated 100 observations from exponential distribution with lamda1=1 as group 1 ...
1answer
500 views

### Can coxph be used for categorical data?

I'm doing some survival analysis and I got the idea to change a binary variable into three-category variable by sub-dividing one category of the binary variable into two new categories. Here's a ...
1answer
190 views

### Version of Mann-Whitney U test, for right-censored data

Is there an equivalent of the Mann-Whitney U test, but for right-censored data? I have right-censored numerical data from two different groups. The mean for one group is higher than the other. I'd ...
2answers
484 views

### how can I focus the log rank test in a selected period of time of follow up?

I am using R survdiff (survival package). I would like to focus the analysis on the first 2 years of my survival curve (that is actually much longer, but with few cases in the long term and with ...
1answer
51 views

### Uneven (right) censoring where the time of truncation is constant

I've collected data comparing the relative success of two different groups of participants on finding the answer to a difficult question. The problem is that not all the participants in the control ...
0answers
83 views

### Is there a reason chi square tests are used over normal tests in survival?

I've been reading and programming a bit about survival, and it seems that a lot of statistics are normally distributed (and thus, their square is chi square distributed). For example, the log rank ...
0answers
513 views

### Reproducing the cox model score test in R

I am using R and would like to recreate by hand the values of the tests. For example, ...
1answer
1k views

### Survival analysis: log rank or ANOVA to compare groups?

If I want to know whether there is a significant difference in age of onset between the 2 groups, should I use ANOVA? My data meet the requirements of an ANOVA test. Or should I use the log rank test, ...
1answer
724 views

### One-Sample Log-rank test statistic

Ok, I am totally confused, this is probably a pure math rather than a statistic question but please enlighten me. I found the logrank statistic formula being reported in the literature in 2 ways, but ...
3answers
350 views

### How can you have p < 0.0001 with a sample size of 89 and a control group of 52?

From Efficacy of monoterpene perillyl alcohol upon survival rate of patients with recurrent glioblastoma (linked from Does Frankincense cure cancer?): Patients and methods It was included 89 ...
0answers
426 views

### Survival probability for a case-control study

I have a case-control study in which 21 patients with a certain clinical outcome and 20 patients without that clinical outcome were (retrospectively) selected from a larger group of patients who were ...
0answers
54 views

### Very puzzling - naming the endpoint of survival analysis

A question that should be straightforward for statisticians but is puzzling me to the point I am nervous. I am doing a PhD in Epidemiology and am going to use Cox regression. The predictor is a ...
1answer
471 views

### Relative Risk with Log-rank test

I always associated/used log-rank test to evaluate Hazard Ratios. However, a well-known professor is using/presenting results of log-rank test for Relative Risk and Risk Ratio. Can anyone explain ...
0answers
795 views

### Matlab survival curve log rank test

I am trying to do survival analysis in matlab and want to calculate log rank test scores among several curves. I found a possible code to do log rank here. But based on its description, it can only do ...
2answers
8k views

### How to calculate the HR and 95%CI using the log-rank test in R?

The R survival package is very useful to do survival analysis. And I know the survdiff function can be used to compare the difference of survival time in two or more groups. And the p-value number can ...
2answers
2k 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) ...
2answers
17k 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) ...
2answers
2k 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?
1answer
473 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, ...
0answers
2k 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 / ...
0answers
85 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 log-...
1answer
2k 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 ...
2answers
664 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 ...
1answer
10k 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 ...
0answers
345 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 ...
4answers
3k 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, ...
2answers
2k 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 ...
2answers
4k 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 ...
1answer
545 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 ...