Lynn Shaffer's Research Essentials
The essentials for interpreting research and statistics
General concepts and discussions on statistics
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 The p-value is derived from the results of a statistical test that assumes the null hypothesis is true. A test statistic is calculated based on the formula for that statistical test using the data collected. The p-value is the probability that the test statistic value is at least as extreme as the…
Developing a Research Question This Word document contains a short guide on developing research questions using PICOT and FINER. A focused and practical research question is the foundation for conducting a successful project. Quick Sample Size Calculator This Excel file can give you an estimate of the number of people (or objects) needed for a…
What It Is A visual graphic which assists in making a calculation. Typically uses two y-axes on either side of a specifically-angled line. The answer is determined by where a line drawn from one y-axis to the other y-axis intersects the specifically-angled line. From the Greek for “law-line.” Why It’s Important Nomograms are convenient in…
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 Related to study power, which is the probability that a statistical test will reject the null hypothesis (usually, “groups are not different”) if in fact the null hypothesis is wrong. Indicates the range of possible results which could occur with repeated, identical studies. Why It’s Important Studies with high precision indicate that…
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…