title: Sample size for ophthalmology studies.
abstract: Knowledge and the usage of actual sample size formulae are a necessity as validity of the inferences from research studies is often dependent on this. This paper explains how sample sizes are calculated. The concept of sampling variation is explained to emphasize the need for its proper calculation. Sample size formulae are explained with examples to provide researchers with a means of calculating the sample sizes for the commonly used study designs. Ophthalmic data are used as examples. It is perceived that this will improve the quality of inferences drawn from ophthalmic research studies.
authors.affiliation: Public Health Ophthalmology Service, L.V. Prasad Eye Institute, L.V. Prasad Marg, Banjara Hills, Hyderabad 500034, India.
authors.forename: T J
authors.initials: TJ
authors.lastname: Naduvilath
authors.forename: R K
authors.initials: RK
authors.lastname: John
authors.forename: L
authors.initials: L
authors.lastname: Dandona
mesh_terms: D006801:Humans; D009885:Ophthalmology / Q000379:methods*; D015203:Reproducibility of Results; D012106:Research / Q000706:statistics & numerical data*; D012107:Research Design; D018401:Sample Size