title: Theoretical implementation of prior knowledge in the design of a multi-scale prosthesis satisfaction questionnaire.
abstract: BACKGROUND
  In product development for lower limb prosthetic devices, a set of special criteria needs to be met. Prosthetic devices have a direct impact on the rehabilitation process after an amputation with both perceived technological and psychological aspects playing an important role. However, available psychometric questionnaires fail to consider the important links between these two dimensions. In this article a probabilistic latent trait model is proposed with seven technical and psychological factors which measure satisfaction with the prosthesis. The results of a first study are used to determine the basic parameters of the statistical model. These distributions represent hypotheses about factor loadings between manifest items and latent factors of the proposed psychometric questionnaire.
  
  
  METHODS
  A study was conducted and analyzed to form hypotheses for the prior distributions of the questionnaire's measurement model. An expert agreement study conducted on 22 experts was used to determine the prior distribution of item-factor loadings in the model.
  
  
  RESULTS
  Model parameters that had to be specified as part of the measurement model were informed prior distributions on the item-factor loadings. For the current 70 items in the questionnaire, each factor loading was set to represent the certainty with which experts had assigned the items to their respective factors. Considering only the measurement model and not the structural model of the questionnaire, 70 out of 217 informed prior distributions on parameters were set.
  
  
  CONCLUSIONS
  The use of preliminary studies to set prior distributions in latent trait models, while being a relatively new approach in psychological research, provides helpful information towards the design of a seven factor questionnaire that means to identify relations between technical and psychological factors in prosthetic product design and rehabilitation medicine.
authors.affiliation: Work and Engineering Psychology, Department of Psychology, Technische Universität Darmstadt, Darmstadt, Germany. schuermann@psychologie.tu-darmstadt.de.
authors.forename: Tim
authors.initials: T
authors.lastname: Schürmann
authors.affiliation: Institute for Mechatronic Systems in Mechanical Engineering, Technische Universität Darmstadt, Darmstadt, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Beckerle
authors.affiliation: Work and Engineering Psychology, Department of Psychology, Technische Universität Darmstadt, Darmstadt, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Preller
authors.affiliation: Work and Engineering Psychology, Department of Psychology, Technische Universität Darmstadt, Darmstadt, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Vogt
authors.affiliation: Institute Humans in Complex Systems, School of Psychology, University of applied Arts and Sciences Northwestern Switzerland, Olten, Switzerland.
authors.forename: Oliver
authors.initials: O
authors.lastname: Christ
mesh_terms: D000671:Amputation, Surgical / Q000523:psychology*; D001186:Artificial Limbs; D001499:Bayes Theorem; D006801:Humans; D007802:Language; D015233:Models, Statistical; D017060:Patient Satisfaction; D011336:Probability; D011474:Prosthesis Design; D011594:Psychometrics / Q000379:methods*; D011795:Surveys and Questionnaires
keywords: Bayesian inference; Lower limb amputation; Prosthetics; Psychological adjustment