Multistage sampling is carried out in stages using smaller and smaller sampling units at subsequent stages. In a two-stage sampling design, a sample of primary units is selected and then another sample of secondary units is selected within each primary unit. Working efficiency of a nationalised bank can be found by smaller sampling units at every stage as one moves up the hierarchy. Area sampling is used when no complete frame of reference is available by dividing the total area under investigation into small sub-areas which are sampled. Quota sampling is a non-probability sampling technique wherein the collected sample has the same proportions of individuals as the entire population with respect to known characteristics, traits or focused phenomenon. Sequential sampling is a non-probability sampling technique done in a sequence wherein a single or a group of subjects is selected in a given time interval, studied, and results analyzed; then another group of subjects is selected if needed and so on.