Lynn Shaffer's Research Essentials
The essentials for interpreting research and statistics
General concepts and discussions on research
What It Is Type II error, also known as beta error, can occur with classical (frequentist) statistical testing. Before the statistical test is conducted, you select the value of the p-value that will determine whether you reject the null hypothesis (usually of no difference between groups). A customary p-value level for rejecting the null hypothesis…
What It Is Many clinical or observational research studies involve regression models. These models employ statistical methods to examine whether particular factors have an association with an outcome. If there are multiple factors of interest in the model, the statistical methods allow for determining whether they have a relationship with the outcome even after considering…
What It Is Good Clinical Practices is a set of guidelines produced by the International Conference on Harmonisation for the conduct of clinical trials. They cover design, ethics, conduct, monitoring and reporting of trials. Why It’s Important Consistent standards for the conduct of clinical trials should result in reliable and high quality evidence produced by…
What It Is When outcomes are of interest but are rare, they are combined into one “yes/no” category to create a general outcome that is more frequent. That is, as soon as one of the outcomes occurs, the composite outcome changes from “no” to “yes.” Why It’s Important The advantage to investigators conducting a randomized…
What It is Patients to be enrolled in a trial are taken a few at a time, depending on the number of study groups – this is called a “block.” Within this small number (typically <10), all possible orderings of the study groups are spelled out. (e.g., for a block size of four patients in…
What It Is A separate randomization sequence (allocation, list) is generated for each subgroup of participants to be enrolled in a clinical trial. Why It’s Important Since it’s a chance procedure, simple randomization may still produce study groups that are not balanced or equivalent with respect to a key factor that affects the outcome. When…
Scroll down to the bottom of this post for the essentials. At last we come to a trial which was published within the last year (October 2019), in the American Journal of Perinatology. The present trial, which I’ll refer to as the “confirmatory trial,” was meant to confirm the results of the Meis trial (see…
What It Is Random assignment to study group of later participants is partly based on the assignment received by previously-enrolled participants. This is done to achieve the intended proportion of participants in each study group (e.g., 50% control and 50% experimental). Why It’s Important Simple randomization does not guarantee that the intended proportion of participants…
What It Is Applies to randomized trials. Every effort is made to include data from all randomized patients in the statistical analysis, according to the group to which they were originally randomized. Why It’s Important Randomization assigns patients to groups based on chance, increasing the likelihood that the people across study groups are equivalent with…
Allocation concealment Composite outcome Confounder, Confounding Ecologic Study, Ecologic Fallacy Files for Downloading FINER for Research Questions Good Clinical Practices Intention to treat Interaction Intermediate Outcome Likelihood to Help or Harm Model (Statistical; Regression) Nomogram Number Needed to Treat (NNT), Number Needed to Harm (NNH) PICOT Research Question p-value Precision (of a study) Predictive Value…