A project was considered "medium" when its total project cost was 20–100 million baht with 50–200 workers, and considered "large" when total project cost was greater than 100 million baht with more than 200 workers. Several manners were used to distribute the questionnaires to the respondents. Nevertheless, to motivate the respondents to participate in the survey, face-to-face or direct delivery was preferred. Doing so improved the response rate.