split-half reliability
a measure of the internal consistency of surveys, psychological tests, questionnaires, and other instruments or techniques that assess participant responses on particular constructs. Split-half reliability is determined by dividing the total set of items (e.g., questions) relating to a construct of interest into halves (e.g., odd-numbered and even-numbered questions) and comparing the results obtained from the two subsets of items thus created. The closer the correlation between results from the two versions, the greater the internal consistency of the survey or instrument. The reliability of the total survey can be determined by applying the Spearman–Brown prophecy formula.