How well do investigators estimate results in advance? A methodological study from a multinational epidemiological survey on hip fracture risks.

The aim of the present study was to compare the factual results with the perception of results by the expert investigators involved in a major epidemiological study on risk factors for hip fracture, the Mediterranean Osteoporosis Study (MEDOS), and to do so before the actual results were known. A selection of 30 questions were used from the original MEDOS questionnaire to obtain estimates of selected key risk factors from the 14 participating experts. Ten investigators participated, six of whom filled out the questionnaire completely; these six questionnaires were used for the analysis. The population was estimated to be younger, to have better functional capacity, and to be more subjected to preventive activities than the actual survey data showed. Several methodological problems are explored.