The previous has shown that the sampling units were drawn prior to the drawing of the actual sample and has a fixed size. But the sequential sampling known as sampling analysis differs from the previous samples in the sense that it does not make an advance determination of the sample size. In this case the researcher obtains measurements on one unit or the population at a single time. A group of population units is also measured at a time. The measurement of each group are cumulated. With the probable error and the cumulated results the size of the sample can be decided. If the error is too large the study of additional groups continues until the standard error is reduced to a minimum level.
The sample size may vary according to the need of the management and standard error. It is not fixed in test the hypotheses sequential sampling reduces the required sample size as compared to the fixed sampling. When the sequential sampling is applied the survey costs may be reduced. The utility of sequential sampling in marketing is not very useful because there is need of a randomly selected sample or cross section study. No small group of sample will be sufficient. There may be need of additional groups of samples to reduce standard error which may involves more cost. By the time the nest sample is taken into study the report of the previous study may be outdated. Considering the utility of the continuing sampling the sequential sample is utilized in the marketing study.