Guttman and his contributions to measurement theory

Louis Guttman was a prominent psychologist and researcher who advanced measurement theory by developing methods to assess whether survey items reliably measure a specific trait or concept. His key contribution, the Guttman scale, is a method to design questionnaires where agreement with more difficult items implies agreement with all easier ones, creating a clear hierarchical pattern. This helps ensure the measurement is consistent and meaningful. His work improved the reliability and interpretability of test scores in social sciences, providing a structured way to gauge attitudes, abilities, or opinions accurately.