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Some authors use the term Cox proportional hazards model even when specifying the underlying hazard function, [14] to acknowledge the debt of the entire field to David Cox. The term Cox regression model (omitting proportional hazards ) is sometimes used to describe the extension of the Cox model to include time-dependent factors.
Cox's theorem, named after the physicist Richard Threlkeld Cox, is a derivation of the laws of probability theory from a certain set of postulates. [ 1 ] [ 2 ] This derivation justifies the so-called "logical" interpretation of probability, as the laws of probability derived by Cox's theorem are applicable to any proposition.
A vertical drop indicates an event. In the aml table shown above, two subjects had events at five weeks, two had events at eight weeks, one had an event at nine weeks, and so on. These events at five weeks, eight weeks and so on are indicated by the vertical drops in the KM plot at those time points.
Kaplan-Meier curve illustrating overall survival based on volume of brain metastases.Elaimy et al. (2011) [6] In its simplest form, the hazard ratio can be interpreted as the chance of an event occurring in the treatment arm divided by the chance of the event occurring in the control arm, or vice versa, of a study.
R 2 N, proposed by Nico Nagelkerke in a highly cited Biometrika paper, [4] provides a correction to the Cox and Snell R 2 so that the maximum value is equal to 1. Nevertheless, the Cox and Snell and likelihood ratio R 2 s show greater agreement with each other than either does with the Nagelkerke R 2. [1]
In statistics, the Box–Cox distribution (also known as the power-normal distribution) is the distribution of a random variable X for which the Box–Cox transformation on X follows a truncated normal distribution. It is a continuous probability distribution having probability density function (pdf) given by
The logrank test statistic compares estimates of the hazard functions of the two groups at each observed event time. It is constructed by computing the observed and expected number of events in one of the groups at each observed event time and then adding these to obtain an overall summary across all-time points where there is an event.
If the chance of hits is nine out of ten, but the probability of a kill with a hit is 0.5, then the P k becomes 0.45 or 45%. This reflects the fact that even modern guided warheads may not always destroy a hit target such as an aircraft , missile or main battle tank .