Réliabilitas (statistika): Béda antarrépisi

 

Dina elmu [[experiment|percobaan]], '''reliabilitas''' nyaeta ukuran tes nu masih keneh angger sanggeus tes dipigawe sababaraha kali kana subyek nu sarua dina kaayan nu ampir sarua oge. Hij percobaan bisa diandelkeun lamun hasilna angger dina unggal ukuran, sarta teu bisa diandelkeun lamun hasilna beda.

==Estimation==

 

Reliability may be estimated through a variety of methods that fall into two types: Single-administration and multiple-administration. Multiple-administration methods require that two assessments are administered. In the ''test-retest'' method, reliability is estimated as the [[Pearson product-moment correlation coefficient]] between two administrations of the same measure. In the ''alternate forms'' method, reliability is estimated by the Pearson product-moment correlation coefficient of two different forms of a measure, usually administered together. Single-administration methods include ''split-half'' and ''internal consistency''. The split-half method treats the two halves of a measure as alternate forms. This "halves reliability" estimate is then stepped up to the full test length using the [[Spearman-Brown prediction formula]]. The most common internal consistency measure is [[Cronbach's alpha]], which is usually interpreted as the mean of all possible split-half coefficients.

Each of these estimation methods is sensitive to different sources of error and so might not be expected to be equal. Also, reliability is a property of the ''scores of a measure'' rather than the measure itself and are thus said to be ''sample dependent''. Reliability estimates from one sample might differ from those of a second sample (beyond what might be expected due to sampling variations) if the second sample is drawn from a different population because the true reliability is different in this second population. (This is true of measures of all types--yardsticks might measure houses well yet have poor reliability when used to measure the lengths of insects.)