关于量表的信度和效度

On the Reliability and the Validity of a Scale

使用平行信度测定法、2组顺向问题平行信度测定法、两样本t检验法、典型相关法、因子分析法、克朗巴赫系数α值计算法 ,以及Theta系数和Omega系数计算法 ,论述反向问题对信度的影响及其处理技巧 ;介绍对调查问卷中的问题进行检验的方法 ;研究和比较评价量表信度和效度的各种方法 ;提出 2组顺向问题平行信度测定法。结果显示 ,以“北京地区农村医生培养问卷调查表”为依据 ,给出对问卷中反向问题处理前后的克朗巴赫系数α值的变化 ;使用两样本t检验方法对每个问题的临界比率 (criticalratio)检验后 ,筛选掉 2个问题 ,筛选后的克朗巴赫系数α值(0 .8993 )比筛选前的 (0 .892 9)略高 ;2组顺向问题平行信度测定法比较精确 (r1=0 .83 2 ) ;对问卷调查表的各个模块分别计算了克朗巴赫系数α、Theta系数、Omega系数 ,对总表除计算上述系数外 ,还计算了 2组顺向问题平行信度 ,它们的值分别是 0 .8993、0 .881 3、0 .95 65和 0 .82 3 0 ,所有的信度指标都表明该调查问卷具有非常高的信度 ;为简便计 ,选择表中的 1个模块 (“本科毕业生去留原因” ,包括 1 0个问题 )为例 ,使用因子分析法得到十分清晰的统计结构 ,它们表明该模块中的问题既有看得见摸得着的实际问题 ,也有认识上和看法上的问题。

The object of the reseach was to describe the effect of the negative questions in a scale on the reliability of the scale and the procedure for recoding the negative questions as well as the hypothesis testing method for the questions in a scale, to investigate and to compare the reliability of a scale obtained with different methods, to compute the parallel reliability between two groups of the positive questions in a scale, to analyze the validity of a scale. The method of the parallel reliability, the method of the parallel reliability between two groups of the positive questions, the indpendent t test method, the canonical correlation, the factor analysis, the methods of computing the Cronbach's coefficient α , the Theta coefficient θ and the Omega coefficient Ω were used. ① Based on the surveillance data of 'The Scale of Training the Rural Doctors in Beijing', the comparison of the Cronbach's coefficient α before and after recoding the negative questions was made. ② By using independent t test to test the null hypothesis of the critical ratio of every question respectively, two questions were sieved and the Cronbach's coefficient rose from 0.892 9 to 0.899 3 after sieving. ③ The simple parallel reliability ( r 1=0.602 7) was much less trustworthy than the parallel reliability between two groups of the positive questions( r p=0.832). ④ The following indicates the whole scale, α =0.899 3, θ = 0.881 3, Ω =0.956 5 and r p =0.823 0 which showed the scale had excellent reliability. ⑤ For the convenience of discussion, we used one model of the scale named 'the reasons of the rural doctors to stay in village or to leave from village' to obtain a distinct statistic structure with the factor analysis method, which showed that the questions in the model could be divided into two groups: one for practical questions, the other rational questions. Endpoints: ① It is important to recode the negative questions in the scale, to compute the reliability and the validity of the scale after sieving the questions without significance. ② It is trustworthy to assess the reliability of the scale with α , θ , Ω and the parallel reliability between two groups of the positive questions except the simple parallel reliability. ③ The statistical structure of the scale obtained by the factor analysis has a very distinct structure, but not unique. The explanation of the statistical structure is based not only upon the statistics but also upon the professional knowledge. And the statistical structure can be a clue to modify the scale.