Calculating sample size for means Afshin Ostovar Bushehr University of Medical Sciences

Principles of Sample Size 1. Variability 2. Effect size 3. Significance level 4. Power of the test 5. Type of the test

Type of the test  Estimation of a mean  Comparing with a constant  Comparing two independent means  Comparing two dependent means  Comparing many independent means

Type of the test  Estimation of a mean  Comparing with a constant  Comparing two independent means  Comparing two dependent means  Comparing many independent means

Estimation of mean Variability Significance Level Difference Standardized effect size

Type of the test  Estimation of a mean  Comparing with a constant  Comparing two independent means  Comparing two dependent means  Comparing many independent means

Comparing with a constant Variability Difference Standardized effect size Significance Level Power of the Test

Type of the test  Estimation of a mean  Comparing with a constant  Comparing two independent means  Comparing two dependent means  Comparing many independent means

Comparing two independent groups Variability Difference Standardized effect size Significance Level Power of the Test Mean in group 1 Mean in group 2

Type of the test  Estimation of a mean  Comparing with a constant  Comparing two independent means  Comparing two dependent means  Comparing many independent means

Comparing Dependent Means Variability Difference Standardized effect size Significance Level Power of the Test

Comparing Dependent Means Variability Difference Standardized effect size Significance Level Power of the Test Mean in group 1 Mean in group 2

Type of the test  Estimation of a mean  Comparing with a constant  Comparing two independent means  Comparing two dependent means  Comparing many independent means

Comparing many independent means 1. Calculate effect size: d = δ/σ 2. Adjustment to formula

Adjustment of effect size