Paek Insu
Florida State University, Tallahassee, FL, USA.
Educ Psychol Meas. 2016 Apr;76(2):205-230. doi: 10.1177/0013164415588133. Epub 2015 May 24.
The effect of guessing on the point estimate of coefficient alpha has been studied in the literature, but the impact of guessing and its interactions with other test characteristics on the interval estimators for coefficient alpha has not been fully investigated. This study examined the impact of guessing and its interactions with other test characteristics on four confidence interval (CI) procedures for coefficient alpha in terms of coverage rate (CR), length, and the degree of asymmetry of CI estimates. In addition, interval estimates of coefficient alpha when data follow the essentially tau-equivalent condition were investigated as a supplement to the case of dichotomous data with examinee guessing. For dichotomous data with guessing, the results did not reveal salient negative effects of guessing and its interactions with other test characteristics (sample size, test length, coefficient alpha levels) on CR and the degree of asymmetry, but the effect of guessing was salient as a main effect and an interaction effect with sample size on the length of the CI estimates, making longer CI estimates as guessing increases, especially when combined with a small sample size. Other important effects (e.g., CI procedures on CR) are also discussed.
文献中已对猜测对系数α点估计的影响进行了研究，但猜测及其与其他测验特征的相互作用对系数α区间估计量的影响尚未得到充分研究。本研究从覆盖率（CR）、区间长度以及区间估计不对称程度这几个方面，考察了猜测及其与其他测验特征的相互作用对系数α的四种置信区间（CI）程序的影响。此外，还研究了数据符合基本tau等价条件时系数α的区间估计，作为对存在考生猜测的二分数据情况的补充。对于存在猜测的二分数据，结果并未显示出猜测及其与其他测验特征（样本量、测验长度、系数α水平）的相互作用对CR和不对称程度有显著负面影响，但猜测作为主效应以及与样本量的交互效应，对CI估计区间长度有显著影响，随着猜测增加，CI估计区间变长，尤其是在样本量较小时。还讨论了其他重要影响（如CI程序对CR的影响）。
