Analysis of a questionnaire for visual comfort assessments: Effects of question formats

This study tests two sets of questionnaires to collect subjective lighting assessments. The questionnaires, one using semantic differentials and the other using Likert-type statements, were presented to 48 participants to compare the differences due to the question format. Experiments were performed in a climate chamber simulating an open-plan office. In a randomized order, participants were exposed to three temperatures (20 °C, 25 °C, and 30 °C) while the artificial lighting was constant (550 lux, 3200 K). Light perception, visual comfort, and acceptability were assessed through 13 items using 7-point scales. Overall, the statement format had higher internal consistency than the semantic differential format. Questions about visual comfort seemed to be reliable under both questionnaire formats, while further development of questions about perception is needed to increase their internal consistency. Although most of the answers were not different due to the questionnaire format (n_average= 61.5%), 38.5% of the answers were different, and the changes were small or moderate and statistically significant in eight items. Further analysis compared the effect of the temperature on lighting evaluations. Our results contribute to a better understanding of the implications of formulating questions on subjective responses and might help develop questionnaires for the field of visual comfort.