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取代还是共存——信度估计系数阿尔法与欧米伽

Replace or Coexist —Cronbach’s Alpha and McDonald’s Omega

Psychology of China / 2022,4(8): 954-961 / 2022-09-05 517 2956

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• Authors: 高清辉
• Information:

  厦门大学，厦门

• Keywords:
  Reliability estimation; Cronbach’s α; MacDonald’s ω
  信度估计; 克隆巴赫α; 麦克唐纳ω
• Abstract: Coefficient Cronbach’s α is the most widely used for estimating reliability. Researchers have used the index extensively in the papers that need to report its reliability, but many scholars have also questioned it. The α coefficient is used as reliability and must satisfy the “essential tau-equivalence” assumption. This assumption is too strict and difficult to meet, and its violation may lead to α overestimating or underestimating the reliability. Using Cronbach’s α to estimate internal consistency is inappropriate. The acceptable lower bound to the reliability of a test is often set empirically, and there is no precise standard. Researchers increase the α value by deleting items, which may also lead to a decrease in the actual reliability of the scale. Although these problems exist, α has been widely used in related research for a long time. This is due to the following reasons: many research fields involve reporting reliability coefficients, researchers have not been taught how to use α correctly for a long time; in addition, standard statistical software has the function of calculating α, which is convenient for calculation; the editors also have requirements for reporting α in the paper. McDonald pointed out that α is a particular case of MacDonald’s ω, and ω becomes α when the “essential tau-equivalence” is satisfied. ω is better than α when the “essential tau-equivalence” cannot be satisfied in reliability estimation. However, the calculation of ω must use confirmatory factor analysis (CFA), which is challenging to implement in the pre-computer era. Researchers have gradually started to use ω instead of α in their research, and more and more people have accepted ω. However, whether MacDonald’s ω should be used instead of Cronbach’s α, there is still a heated debate in the academic community. Opinions on ω mainly focus on the fact that the actual values of ω and α are not significantly different in the calculation. That ω may show more estimation failures when the sample size and overall reliability are small. It is unreasonable to abandon α or be unwilling to move forward and stick to α. In future research, use McDonald’s omega and Cronbach’s alpha for reliability estimation to coexist for a long time and complement each other. 在众多信度指标中，克隆巴赫α （Cronbach’s α ）系数最为常用，但α 系数在使用中常常忽视重要的“基本τ 等价”假设，导致α 系数并非真正的信度；并且存在着误用与滥用、阈值不确定等问题，受到很多批评，被长期广泛应用是因其易于计算、易于理解等特性。麦克唐纳ω 克服了α 系数的上述缺点，信度估计上明显优于α 系数，但麦克唐纳ω 也存在计算要求较高等缺点，尚无法取代克隆巴赫α 。两个信度指标ω 与α 将长期共存，在研究报告中应同时提供ω 与α 的数值，互相补充。
• DOI: https://doi.org/10.35534/pc.0408114
• Cite: 高清辉．取代还是共存——信度估计系数阿尔法与欧米伽［J］．中国心理学前沿，2022，4（8）：954-961．