Effect Size Guidelines, Sample Size Calculations, and Statistical Power in Gerontology.

Only 42% (465/1,108) of the studies in the analysis were appropriately powered to detect a medium effect, although based on the contour-enhanced funnel plot ( Figure 3A ), there did not appear to be an overrepresentation of just-significant ( p values between .05 and .01, represented by the red area of the figure) or marginally significant ( p values between .10 and .05, represented by the orange area of the figure) results, suggesting that inflation bias in gerontological individual differences research is unlikely.

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