## sample size calculation: why & how

- what about my sample size ?
- more is better ≡ observation → information
- but increasingly less so
- but limited resources (time/money)
- but ethical and practical considerations

- how many is good enough ?
- depends on what you want

- workshop → how to calculate it ?
- understand the reasoning
- apply for simple but common situations

- not one simple formula for all → GPower to the rescue