A comparison of open-ended and closed questions in the prediction of mental health

The statistical benefit of adding open-ended questions to closed questions was evaluated in a survey of 643 participants. The construct of coping was chosen as the measurement domain. Open and closed questions were used to predict mental health a year later. Verbatim responses to open questions were reliably coded (ICC = 0.92), but they did not increase the statistical prediction of measures of mental health beyond the contribution of closed questions. Open-ended questions provided more in-depth information than closed questions, but at the cost of more missing data and less degrees of freedom. The benefit of using open-ended in addition to standard closed questions was thus practically nil, hence questioning the use of qualitative information gathering in surveys for the purpose of statistical prediction.