Box.

Examples of how the research design of a study may be described

Non-empirical or empirical

Case-based or sample-based

Observational or interventional

Retrospective or prospective

Cross-sectional or longitudinal

Uncontrolled or controlled

Single arm or multiple arm

Nonrandomized or randomized

Crossover or parallel group

Non-blind, single-blind, or double-blind

Superiority or non-inferiority

Exploratory (hypothesis-generating) or confirmatory (hypothesis-driven)