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

VariabilitySignificance 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