Steekproefgroottes in plaaslik gepubliseerde psigologiese navorsing

Abstract

English

Die krag van 'n statistiese toets is onder meer 'n funksie van die effekgrootte (d.i. die afwyking van die ware populasiewaarde van dié in die nulhipotese gepostuleer) en steekproefgrootte. In hierdie ondersoek is kragwaardes vir die opsporing van klein, matige en groot effekgroottes soos deur Cohen gedefinieer, bepaal vir elke artikel wat enige van die standaard- statistiese beduidendheidstoetse gebruik het en van 1980 tot 1989 in die Suid-Afrikaanse Tydskrif vir Sielkunde gepubliseer is. 'n Tweekantige toets met α = 0,05 is veronderstel. Die resultate suggereer dat die gemak waarmee proefpersone gehanteer word 'n rol speel in die steekproefgrootte wat plaaslike navorsers gebruik. Gevolglik is die krag van eksperimentele ondersoeke geneig is om te laag te wees, terwyl die hoër krag by groter steekproewe nie by die interpretasie van statisties beduidende resultate in berekening gebring word nie. Wanneer groot steekproewe moeilik haalbaar is, word Cohen se strategie vir die bepaling van die optimale steekproefgrootte aanbeveel om te voorkom dat navorsing met onaanvaarbaar lae krag onderneem word. Hierdie prosedure vereis dat die prakties of teoreties betekenisvolle effekgrootte en die krag om dit op te spoor vooraf gespesifiseer word. Wanneer groot steekproewe maklik hanteerbaar is, word Serlin en Lapsley se benadering voorgestel waarvolgens saamgestelde nulhipoteses wat die betekenisvolle effekgrootte reflekteer, getoets word.

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