The Haybittle–Peto boundary is a rule for deciding when to stop a
clinical trial
Clinical trials are prospective biomedical or behavioral research studies on human subject research, human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel v ...
prematurely. It is named for
John Haybittle and
Richard Peto.
The typical clinical trial compares two groups of patients. One group is given a
placebo
A placebo ( ) can be roughly defined as a sham medical treatment. Common placebos include inert tablets (like sugar pills), inert injections (like saline), sham surgery, and other procedures.
Placebos are used in randomized clinical trials ...
or conventional treatment, while the other group of patients are given the treatment that is being tested. The investigators running the clinical trial will wish to stop the trial early for ethical reasons if the treatment group clearly shows evidence of benefit. In other words, "when early results proved so promising it was no longer fair to keep patients on the older drugs for comparison, without giving them the opportunity to change."
The Haybittle–Peto boundary is one such
stopping rule
In probability theory, in particular in the study of stochastic processes, a stopping time (also Markov time, Markov moment, optional stopping time or optional time ) is a specific type of "random time": a random variable whose value is interpre ...
, and it states that if an
interim analysis shows a probability equal to, or less than 0.001 that a difference as extreme or more between the treatments is found, given that the
null hypothesis
The null hypothesis (often denoted ''H''0) is the claim in scientific research that the effect being studied does not exist. The null hypothesis can also be described as the hypothesis in which no relationship exists between two sets of data o ...
is true, then the trial should be stopped early. The final analysis is still evaluated at the normal level of significance (usually 0.05). The main advantage of the Haybittle–Peto boundary is that the same threshold is used at every interim analysis, unlike the
O'Brien–Fleming boundary, which changes at every analysis. Also, using the Haybittle–Peto boundary means that the final analysis is performed using a 0.05 level of significance as normal, which makes it easier for investigators and readers to understand. The main argument against the Haybittle–Peto boundary is that some investigators believe that the Haybittle–Peto boundary is too conservative and makes it too difficult to stop a trial.
Synonyms
* Peto boundary
* Peto method
* Peto criteria
See also
*
Pocock boundary
References
{{DEFAULTSORT:Haybittle-Peto boundary
Clinical research
Sequential experiments