Secondary studies synthesise the results from primary studies: Systematic reviews have a defined set criteria for finding and including primary studies for critical analysis. Methodology from these primary studies is often evaluated and results synthesised. Meta-analysis is a statistical procedure for combining quantitate data from studies evaluating the same outcomes (e.g. data from a study of a large population showing a strong correlation and data … Continue reading Secondary studies

Diagnostic and screening tests (e.g. HIV blood test, colonoscopy) respectively confirm a condition or detect high risk individuals. Measures such as sensitivity and predictive values are used describe these tests. They can help calibrate tests (e.g. set criteria for positive diagnosis) or indicate the suitability of tests to different applications (i.e. a less accurate but cheaper test may be more suited to screening than diagnosis). … Continue reading Diagnostic & screening tests

Observational (or non-experimental) studies have no intervention and purely observe changes in one characteristic (e.g. smoking) compared to another (e.g. lung cancer) in the natural world. These studies can be classed into analytical studies, which aim to determine correlation and causality, or descriptive which merely reports a certain situation. Analytical studies Analytical (analytic) studies examine populations and analyze if there is a causal correlation between … Continue reading Observational studies

Interventional (experimental) studies see if an intervention that purposefully changes some aspect of a subject’s status (e.g. ingesting a drug) affects an outcome (e.g. recovery from disease). To ensure interventional studies are valid, randomization and blinding is often utilised, with randomized control trials (RCTs) being the gold-standard of clinical trials: Random allocation: Subjects are randomly allocated to different treatment groups so that baseline characteristics of … Continue reading Interventional studies

Primary (or empirical) studies are first-hand investigations based on direct observations and can be broadly classed as interventional or observational. They can be performed on animals as well as humans and also include laboratory studies. Observational studies can be subdivided into analytical (analytic) and descriptive studies while all experimental studies are analytical. Continue reading Primary studies