Statistical signficance Likelyhood that the result from a study is true for the entire population -> p-value (p<0.05/0.01 often alpha level, below = significant)

Effect size How strong is the effect if it exists ?

Statistical power How likely it is that the study can distinguish between an actual effect from chance. (Target:~80%)

Sample size No right answers. Sample size determines statistical power. Big enough to reach the needed statistical power, to big = inefficient.