BEFORE GOING INSIDE THE QUESTION, ONE HAS TO UNDERSTAND THE CONCEPT OF SURVEY. SURVEY CAN BE DEFINED AS AN INVESTIGATION OF THE OPINIONS OR EXPERIENCE OF A GROUP OF PEOPLE BASED ON SERIES OF QUESTIONS. THERE RAE MANY TYPES OF SURVEYS. 1: ACCORDING TO INSTRUMENTATION; A. QUESTIONNAIRES, B. INTERVIEWS. 2: ACCORDING TO THE SPAN OF TIME INVOLVED; A.CROSS-SECTIONAL SURVEYS, B.LONGITUDINAL SURVEYS. QUESTIONNAIRE: IT IS A PAPER AND PENCIL INSTRUMENT THAT IS ADMINISTERED TO THE RESPONDENTS. THESE ARE USUALLY CLOSE-ENDED QUESTIONS WHICH ARE FOLLOWED BY RESPONSE OPTIONS. IN STATISTICS TERMINOLOGY WE HAVE THE TERM "NON-RESPONSE BIAS". NON-RESPONSE BIAS IS USUALLY INTRODUCED AT TIMES WHEN THE LARGE FRACTION OF THE SAMPLED FAILS TO GIVE A RESPONSE TO A SURVEY OR OTHER QUANTITIES.
