In attempting to move questionnaire design from art to science, researchers use different evaluation techniques to help determine how well questions are working. Techniques such as behavior coding, respondent debriefing, interviewer debriefing, cognitive interviewing, and nonresponse analysis all provide information to help the questionnaire designer assess whether respondents understand questions as intended and whether they are able to provide adequate answers to them. In 1994, Presser and Blair evaluated some of these methods, concluding that behavior coding provided more reliable diagnoses of question difficulties than conventional pretests involving a small number of interviewers followed by an interviewer debriefing.