Jämför metoder

	Effektstorlek	Statistisk styrka och stickprovsstorlek
Ämnesområde	Forskningsstatistik	Forskningsstatistik
Familj	Process / pipeline	Process / pipeline
Ursprungsår	1988	1988
Upphovsperson	Jacob Cohen	Jacob Cohen
Typ	Concept	Concept
Ursprungskälla	Cohen, J. (1988). Statistical Power Analysis for the Behavioral Sciences (2nd ed.). Lawrence Erlbaum Associates. ISBN: 0-8058-0283-5	Cohen, J. (1988). Statistical Power Analysis for the Behavioral Sciences (2nd ed.). Lawrence Erlbaum Associates. ISBN: 0-8058-0283-5
Alias	ES, Cohen's d, standardized effect, practical significance	power analysis, sample size calculation, 1 minus beta, sensitivity
Närliggande	4	4
Sammanfattning	Effect size quantifies the magnitude of a research finding independent of sample size. While a p-value tells you whether a result is statistically significant, an effect size tells you how big the result is. Jacob Cohen formalized effect size measurement in behavioral sciences (1988), establishing standard benchmarks (small = 0.2, medium = 0.5, large = 0.8 for Cohen's d). Effect sizes are essential for meta-analysis, power analysis, and communicating the practical importance of research findings.	Statistical power is the probability of detecting a true effect if it exists (1 − β). Power analysis determines the sample size required to detect a hypothesized effect size with specified Type I error (α) and Type II error (β) rates. Introduced by Jacob Cohen (1988), power analysis is foundational to research design: underpowered studies produce inflated effect size estimates and are unlikely to replicate. The standard benchmark is 80% power (β = 0.20), though critical studies may require 90% power.