Questionnaire design in market research is a huge topic. Questions need to be very carefully thought through and need to be ordered and asked in such a way that the person contacted is not intimidated or alienated. Quantitative questions are by definition more exact than qualitative questions. One method for overcoming a respondent's inability to verbalize answers involves projective techniques. Projective techniques use a vague question or stimulus and attempt to project a person's attitudes from the response. Embarrassing questions dealing with personal or private matters should be avoided. Interviewing competitors is a necessary feature of Commercial due diligence (CDD). Focus groups are especially useful in testing new ideas, evaluating services or understanding consumer behaviour and really should be used more often in CDD. Mystery shopping is a way of measuring service quality using covert observation. It is widely used in both private sector and government market research.