What does a log rank test tell you?

The Log Rank Test. The log rank test is a popular test to test the null hypothesis of no difference in survival between two or more independent groups. The test compares the entire survival experience between groups and can be thought of as a test of whether the survival curves are identical (overlapping) or not.

What is the log hazard ratio?

The log hazard ratio (experimental relative to control) is estimated by (O – E)/V, which has standard error 1/√V, where O is the observed number of events on the experimental intervention, E is the logrank expected number of events on the experimental intervention, O – E is the log-rank statistic and V is the variance …

What is the P value in log rank test?

It is a simplified version of a statistic that is often calculated in statistical packages [2]. This gives a P value of 0.032, which indicates a significant difference between the population survival curves. An assumption for the log rank test is that of proportional hazards.

Why is it called the log rank test?

The logrank test, or log-rank test, is a hypothesis test to compare the survival distributions of two samples. The test is sometimes called the Mantel–Cox test, named after Nathan Mantel and David Cox. The logrank test can also be viewed as a time-stratified Cochran–Mantel–Haenszel test.

What is the null hypothesis for a log rank test?

The null hypothesis tested by the log-rank test is that of equal event time distributions among groups. Equality of the distributions of event times implies similar event rates among groups not only for the clinical trial as a whole, but also for any arbitrary time point during the trial.

How do you interpret hazard ratios?

It is the result of comparing the hazard function among exposed to the hazard function among non-exposed. As for the other measures of association, a hazard ratio of 1 means lack of association, a hazard ratio greater than 1 suggests an increased risk, and a hazard ratio below 1 suggests a smaller risk.

What is p value in Kaplan Meier?

The p-value to which you are referring is result of the log-rank test or possibly the Wilcoxon. This test compares expected to observed failures at each failure time in both treatment and control arms. It is a test of the entire distribution of failure times, not just the median.

Is a higher hazard ratio better?

A hazard ratio of one means that there is no difference in survival between the two groups. A hazard ratio of greater than one or less than one means that survival was better in one of the groups.

What kind of test is the log rank test?

Logrank test. The logrank test, or log-rank test, is a hypothesis test to compare the survival distributions of two samples.

When to use logrank for the hazard ratio?

If is the logrank statistic, is the number of events observed, and is the estimate of the hazard ratio, then . This relationship is useful when two of the quantities are known (e.g. from a published article), but the third one is needed. The logrank statistic can be used when observations are censored.

Which is the null hypothesis of the log rank test?

A test that this hazard ratio equals 1 is a test of the null hypothesis of equality of the survival functions of the two groups. The log rank test is essentially equivalent to the score test that the HR=1 in the Cox model, and is commonly used as the primary analysis hypothesis test in randomised trials.

Is the hazard ratio computed at one time point?

The hazard ratio is not computed at any one time point, but includes all the data in the survival curve. Since there is only one hazard ratio reported, it can can only be interpreted if you assume that the population hazard ratio is consistent over time, and that any differences are due to random sampling.