Reducing bias in shopping mall-intercept surveys: The time-based systematic sampling method

Marketing practitioners nowadays often have to base important management decisions on information obtained in research surveys conducted in shopping malls. The shopping mall-intercept survey is a very popular method used by research agencies to gather information of almost all kinds. While the advantages of shopping mall-intercept interviewing are considerable, their adoption without recognition of their shortcomings is not prudent. Selection error, resulting in time sampling bias, occurs in shopping mall-intercept surveys as a result of significant differences between the characteristics of persons visiting a shopping mall at different time segments during a month period. In this empirical study, the authors explain the problem of time-based selection error in mall-intercept data, the failure of common research practices to correct it, and develop a specific time-bias reduction technique.