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Last Updated: 18-09-2019 21:00
Scale Construction Utilising the Rasch Unidimensional Measurement Model
Scales used to measure latent traits like behavioural attitudes are typically measured using classical statistical approaches. However, treating raw scores as interval scales present a fundamental problem when developing measures. To avoid these pitfalls human measurement instruments need to be constructed using Rasch analysis. The Rasch unidimensional model is currently the only method able to transform raw data into abstract equal-interval scales. The objective being for each personality dimension to have all items fit the Rasch model well, with the more endorsable items reliably preceding more difficult to endorse items in the direction of increasing levels of the underlying latent construct. Specifically, ensuring that all the items in each measured dimension manifests construct linearity and conjoint additivity. According to this view, if the data fit the model, then a scale with linearity and conjoint additivity will have been developed.