I have created an Excel spreadsheet to automatically calculate split-half reliability with Spearman-Brown adjustment, KR-20, KR-21, and Cronbach’s alpha.
The reliability estimates are incorrect if you have missing data.
KRl-20 and KR-21 only work when data are entered as 0 and 1.
Split-half and Cronbach’s alpha work with Likert scale data as well (1, 2, 3, 4, 5, etc).
Only numeric data works with the spreadsheet (don’t enter A, SA, N, SD, D ….enter 5, 4, 3, 2, 1)