Reliability Analysis: Statistics

You can select various statistics that describe your scale, items and the interrater agreement to determine the reliability among the various raters. Statistics that are reported by default include the number of cases, the number of items, and reliability estimates as follows:

Alpha models

Coefficient alpha; for dichotomous data, this is equivalent to the Kuder-Richardson 20 (KR20) coefficient.

Omega models

Estimation of McDonald’s omega to evaluate reliability.

Split-half models

Correlation between forms, Guttman split-half reliability, Spearman-Brown reliability (equal and unequal length), and coefficient alpha for each half.

Guttman models

Reliability coefficients lambda 1 through lambda 6.

Parallel and Strict parallel models

Test for goodness of fit of model; estimates of error variance, common variance, and true variance; estimated common inter-item correlation; estimated reliability; and unbiased estimate of reliability.

Descriptives for

Produces descriptive statistics for scales or items across cases.

Item

Produces descriptive statistics for items across cases.

Scale

Produces descriptive statistics for scales.

Scale if item deleted

Displays summary statistics comparing each item to the scale that is composed of the other items. Statistics include scale mean and variance if the item were to be deleted from the scale, correlation between the item and the scale that is composed of other items, and Cronbach's alpha if the item were to be deleted from the scale.

Summaries

Provides descriptive statistics of item distributions across all items in the scale.

Means

Summary statistics for item means. The smallest, largest, and average item means, the range and variance of item means, and the ratio of the largest to the smallest item means are displayed.

Variances

Summary statistics for item variances. The smallest, largest, and average item variances, the range and variance of item variances, and the ratio of the largest to the smallest item variances are displayed.

Correlations

Summary statistics for inter-item correlations. The smallest, largest, and average inter-item correlations, the range and variance of inter-item correlations, and the ratio of the largest to the smallest inter-item correlations are displayed.

Covariances

Summary statistics for inter-item covariances. The smallest, largest, and average inter-item covariances, the range and variance of inter-item covariances, and the ratio of the largest to the smallest inter-item covariances are displayed.

Inter-Item

Produces matrices of correlations or covariances between items.

ANOVA Table

Produces tests of equal means.

F test

Displays a repeated measures analysis-of-variance table.

Friedman chi-square

Displays Friedman's chi-square and Kendall's coefficient of concordance. This option is appropriate for data that are in the form of ranks. The chi-square test replaces the usual F test in the ANOVA table.

Cochran chi-square

Displays Cochran's Q. This option is appropriate for data that are dichotomous. The Q statistic replaces the usual F statistic in the ANOVA table.

Hotelling's T-square

Produces a multivariate test of the null hypothesis that all items on the scale have the same mean.

Tukey's test of additivity

Produces a test of the assumption that there is no multiplicative interaction among the items.

Intraclass correlation coefficient

Produces measures of consistency or agreement of values within cases.

Model

Select the model for calculating the intraclass correlation coefficient. Available models are Two-Way Mixed, Two-Way Random, and One-Way Random. Select Two-Way Mixed when people effects are random and the item effects are fixed, select Two-Way Random when people effects and the item effects are random, or select One-Way Random when people effects are random.

Type

Select the type of index. Available types are Consistency and Absolute Agreement.

Confidence interval (%)

Specify the level for the confidence interval. The default is 95%.

Test value

Specify the hypothesized value of the coefficient for the hypothesis test. This value is the value to which the observed value is compared. The default value is 0.

Specifying Statistics settings

This feature requires the Statistics Base option.

1. From the menus choose:

   Analyze > Scale > Reliability Analysis...

2. In the Reliability Analysis dialog, click Statistics.