<P> An example of cluster sampling is area sampling or geographical cluster sampling . Each cluster is a geographical area . Because a geographically dispersed population can be expensive to survey, greater economy than simple random sampling can be achieved by grouping several respondents within a local area into a cluster . It is usually necessary to increase the total sample size to achieve equivalent precision in the estimators, but cost savings may make such an increase in sample size feasible . </P> <P> Cluster sampling is used to estimate high mortalities in cases such as wars, famines and natural disasters . </P> <Ul> <Li> Can be cheaper than other sampling plans--e.g. fewer travel expenses, administration costs . </Li> <Li> Feasibility: This sampling plan takes large populations into account . Since these groups are so large, deploying any other sampling plan would be very costly . </Li> <Li> Economy: The regular two major concerns of expenditure, i.e., traveling and listing, are greatly reduced in this method . For example: Compiling research information about every household in a city would be very costly, whereas compiling information about various blocks of the city will be more economical . Here, traveling as well as listing efforts will be greatly reduced . </Li> <Li> Reduced variability: When estimates are being considered by any other method, reduced variability in results are observed . This may not be an ideal situation every time . </Li> </Ul> <Li> Can be cheaper than other sampling plans--e.g. fewer travel expenses, administration costs . </Li>

Which of the following is not an example of a multistage cluster sample