Internal consistency reliability

Internal consistency is a measure of reliability that assesses the interrelatedness among items within a multi-item measure or tool, such as a patient-reported outcome measure (PROM). It evaluates whether multiple items designed to measure the same underlying concept produce similar scores. A high degree of internal consistency suggests that the items are all measuring the same construct, making the overall scale reliable. There are three types of statistical measures to determine the internal consistency reliability: Cronbach’s alpha, split-half test, and Kuder-Richardson test. The typical measure is the Cronbach’s alpha, which has a range of 0 to 1. The closer to 1, the more reliable the assessment. The scale determines how much agreement each item in a test has. The more agreement, the more the questions are aligned or alike. The scale is as follows: 0.00 to 0.69 = poor alignment, 0.70 to 0.79 = fair alignment, 0.80 to 0.89 = good alignment, 0.90 to 0.99 = strong alignment.