What is a prespecified analysis?
A prespecified subgroup analysis is one that is planned and documented before any examination of the data, preferably in the study protocol. This analysis includes specification of the end point, the baseline characteristic, and the statistical method used to test for an interaction.
What is prespecified secondary analysis?
There are two types of data analyses of randomized clinical trials (RCTs). The primary analyses are pre-specified in the protocol and the findings form the basis for recommendations and clinical decisions. Secondary analyses are supplemental and of various sorts. Although some may be pre-specified, many are not.
What is a priori subgroup analysis?
An a priori subgroup analysis is one that is planned and documented before examination of data, preferably in the study protocol, and ideally includes a hypothesized direction of effect. Subgroup treatment effect interactions identified post hoc must be interpreted with caution.
What is stratified randomization in clinical trials?
Stratified randomization is a two-stage procedure in which patients who enter a clinical trial are first grouped into strata according to clinical features that may influence outcome risk. Within each stratum, patients are then assigned to a treatment according to separate randomization schedules [1].
Why is post hoc analysis bad?
When conclusions are made from post-hoc analyses, there is an inherent bias, as we are able to test the data in any way that produces a favorable result. In many cases, this leads to data dredging or in the worst cases, p-hacking.
What are prespecified outcomes?
A pre-specified outcome is much less likely to give a false-positive result. This ensures a fair picture of the trial results. However, in reality, pre-specified outcomes are often left unreported, while outcomes that were not pre-specified are reported, without being declared as novel.
What is difference between primary and secondary endpoint?
The primary endpoint of a clinical trial is the endpoint for which the trial is powered. Secondary endpoints are additional endpoints, preferably also pre-specified, for which the trial may not be powered.
What is subgroup analysis in meta analysis?
Subgroup analysis is the process of comparing a treatment effect for two or more variants of an intervention-to ask, for example, if an intervention’s impact is affected by the setting (school versus community), by the delivery agent (outside facilitator versus regular classroom teacher), by the quality of delivery, or …
How does stratified randomization work?
In statistics, stratified randomization is a method of sampling which first stratifies the whole study population into subgroups with same attributes or characteristics, known as strata, then followed by simple random sampling from the stratified groups, where each element within the same subgroup are selected …
Why is stratified randomisation used?
Stratified randomization prevents imbalance between treatment groups for known factors that influence prognosis or treatment responsiveness. As a result, stratification may prevent type I error and improve power for small trials (<400 patients), but only when the stratification factors have a large effect on prognosis.