Practice question · Multiple choice
A study with 20 participants finds no significant effect. Why is "there is no effect" the wrong conclusion?
Hints
- Ask what a study with 20 people could have detected if the effect were moderate.
- A null result is compatible with two very different worlds. Name both.
Show the answer
B. Because a small sample may be unable to detect a real effect at all
Why
A null result from an underpowered study is uninformative rather than negative, it is compatible with no effect and with a real effect the design could never see. The fix is to report power or a confidence interval: 'the effect is between −0.1 and +0.5' says something, and 'p > .05' does not.
Practise Sampling and Representativeness
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