What is the statistical method to use in parallel form reliability?

The Spearman-Brown formula is the appropriate statistical method for assessing parallel form reliability. This method is used when we have two different forms of a test that are designed to measure the same construct. Parallel form reliability examines the consistency of scores across these different forms, ensuring that they yield similar results when measuring the same underlying trait.

The Spearman-Brown formula helps in estimating reliability based on the correlation between the two test forms. Specifically, it adjusts the reliability coefficient of a shorter test to estimate the reliability of a longer test, which can be very useful in determining how well the forms align in measuring the same characteristics. This is essential for making sure that the tests are interchangeable and that results can be trusted across different administrations of the tests.

In contrast, Kappa statistics is primarily used for assessing agreement between categorical variables, while the Pearson correlation coefficient measures the linear relationship between two continuous variables. Cronbach's alpha is mainly used for determining the internal consistency of a single test rather than comparing two different forms. Thus, the Spearman-Brown formula is uniquely suited for evaluating parallel form reliability because it directly addresses the correlation needed between these two versions of a test.