|
Factors that affect sample size calculations |
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| Factor |
Magnitude |
Impact on identification of effect |
Required sample size |
|
|
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| P value |
Small |
Stringent criterion; difficult to achieve 'significance' |
Large |
| Large |
Relaxed criterion; 'significance' easier to attain |
Small |
|
| Power |
Low |
Identification unlikely |
Small |
| High |
Identification more probable |
Large |
|
| Effect |
Small |
Difficult to identify |
Large |
| Large |
Easy to identify |
Small |
|
Whitley and Ball Critical Care 2002 6:335 doi:10.1186/cc1521 |
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