special care needs to be taken in order to choose the right sample size. Optimal sample size should provide cost effective survey without deteriorating survey’s analytic potential. What managers and consultants need to have in mind when deciding on sample size1? Firstly, they need to determine the desired confidence interval (CI). Higher CI offers more reliable findings because probability that population parameter exceeds the margin of error is low. CI of 95% is suitable for most occasions. Secondly, managers need to determine desirable maximum margin of error. Higher CI and narrower maximum margin of error require larger sample. In return CSS analytic potential is increased when conducting significance testing and other statistical analysis. General recommendations should be taken into account as well. Sample size will increase with the number of subgroups relevant for analysis (minimal size of the subgroup is n = 30 respondents). Also, the attitude of target population towards the survey subject affects the sample size, because greater variance in attitude requires larger sample size. So when it all boils down, what would be the recommended sample size when conducting CSS in financial services2? • If the target population is expected to be homogenous (e.g., financial service provider’s own customers) and there are only 4-6 subgroups relevant for analysis (such as customer segments) than recommended minimal sample size is N = 600. This allows subgroups to contain n = 100-150 respondents which should be enough for analysis. • In case of a larger number of subgroups (e.g., determined by demographic criteria) and in the case that CSS is addressing more sensitive issue with greater variance (such as customer dissatisfaction) a larger sample is required and the recommended sample size should be N = 1,200 respondents. • If the financial service provider deals with particularly large number of customers that are dis1 Determination of sample size for finite target populations requires different methods than the ones used for determination of sample size for infinite target populations. Therefore, recommendations in reference with the sample size cannot be applied to the CSS in corporate financial services because they are conducted at finite target populations. 2 In case of multinational CSS presented sample sizes refer to the sample size for each country participating in the research project. Therefore, when conducting multinational CSS sample size grows with the expansion of the geographical embracement of survey. Otherwise it would not be possible to compare performance among subsidies operating on foreign markets.
118 Marko Đorđić
persed over a large number of branch offices, than sample size can exceed N = 3,000. Sample size is of vital importance for the success of CSS. No matter how well the survey is designed small sample size can significantly deteriorate its analytical potential.
CSS Implementation Conducting CSS in financial services requires direct contact with large number of actual customers and it is wise to invest additional efforts to ensure flawless execution of the project. It is especially important to: (a) properly train field force, (b) engage specific safety measures, (c) choose the most adequate survey method and (d) properly design questionnaire. There are few factors that should be taken into account in order to select appropriate survey method: (a) objective and purpose of marketing research, (b) attitude of target population towards the research subject, and (c) features of target population. These factors are especially important when conducting CSS with customers of financial service providers, because great care must be taken not to cause any unnecessary disturbance while conducting fieldwork. Following paragraphs examine available survey methods in order to discover the best one for conducting CSS in financial services. In home face-to-face (F2F) interviewing might be the first choice of many. Textbooks and marketing research practice state that F2F interviewing is the best survey method when conducting in depth surveys with strategic analytic potential. This is certainly true because F2F interviews can be very lengthy and provide the possibility to use photos or images within the questionnaire. Also, direct contact between respondents and interviewers may help in creating relaxed atmosphere during the interview and boost respondent’s self confidence. F2F interviewing may be conducted at branch offices as well. Customers may be asked to participate in survey during their stay or after they leave the branch office (i.e. exit pool). However, conducting CSS this way would make the sample representative only for customers that actually visit the branch. Therefore, significant number of customers would be left out from sample. Few other obstacles must be taken into account as well. According to the latest data (European Society for Opinion and Marketing Research (ESOMAR, 2008) the response rate in F2F interviewing is declining. Whether you choose to