Types of study design arranged by level of evidence, from low to high
Scientific information is an economic commodity, and that scientific journals are a medium for its dissemination and exchange. As such it is subject to economic factors that affect the value of scientific information and how it is exchanged.
Retrospective studies are designed to analyse pre-existing data, and are subject to numerous biases as a result. Types of retrospective studies include: case series; retrospective cohort studies; case-control studies
Standardised Mortality Ratio SMR is the ratio of the observed or actual hospital mortality and the predicted hospital mortality for a specified time period.
Error in research can be systematic or random; systematic error is also referred to as bias
Data can be described by different distributions, which has implications for how the data is analysed using statistical methods
Fisher’s Exact Test is to compare categorical data; more complicated to perform than the Chi square test; only generally applicable in 2 x 2 contingency table
Intention to treat (ITT) analysis means all patients who were enrolled and randomly allocated to treatment are included in the analysis and are analysed in the groups to which they were randomized
Meta-analysis is a tool for quantitative systematic review of observational studies and controlled trials that weights available evidence based on the numbers of patients included, the effect size, and often statistical tests of agreement with other trials
Measures if variability describe the average dispersion of data around a mean; most common = range, standard deviation and the standard error of the mean