Thus not all the population eligible to be included in the BCS will be included, these discrepancies do not fall into the realms of sampling error, as the numbers involved are relatively small in comparison to the overall survey. Comparisons between the sample proportions and the census proportions are therefore seen as a valid method of testing the validity and representativeness of the BCS sampling survey. The BCS has been criticised by Genn et al (1987) for missing people living in hostels, bed-sit accommodation and the homeless, who themselves may be some of the highest risk categories in society. A booster sample has been added in recent years of 4,000 ethnic minority people to see if their experiences of crime differ from those of the general population.
A questionnaire-based survey is used for the BCS, as it is the cheapest, quickest and most easily quantifiable form of research methodology for such large-scale social surveys. As Sellitz et al (1976) say " questionnaires can be sent through the post, where as interviewers cannot". A questionnaire also produces very quick and quantifiable data; it is relatively easy to transfer data into a quantifiable form. The BCS offers the respondent a very high degree of anonymity, which in respect of the delicacy of some of the areas covered in the survey is desirable to both parties. The questionnaire-based survey also cuts down the opportunity for interviewer bias and demand characteristics.
Perhaps the most limiting aspect of a questionnaire-based survey is the inability to prompt, probe and clarify certain areas of enquiry. The survey deals in absolutes, and doesn't allow for human emotion and conjecture. The survey also relies upon the self-motivation of the respondents in participating in the survey. In this respect, the sample may not be adequately represented in certain sections of the community. Elliot and Ellingworth (1992) have suggested that in areas of high crime, the population become apathetic to crime, and therefore are less likely to complete a victim survey.
