Modeling item nonresponse in questionnaires

The statistical analysis of empirical questionnaire data can be hampered by the fact that not all questions are answered by all individuals. In this p aper we propose a simple practical method to deal with such item nonrespons e in case of ordinal questionnaire data, where we assume that item nonrespo nse is caused by an incomplete set of answers between which the individuals are supposed to choose. Our statistical method is based on extending the o rdinal regression model with an additional category for nonresponse, and on investigating whether this extended model describes and forecasts the data well. We illustrate our approach for two questions from a questionnaire he ld amongst a sample of clients of a financial investment company.