Explanation
The number of stages involved in the sampling method is partially a function of the number of sampling frame available. If a perfect frame were always available complete with all the associated information one might want for purposes of clustering and / or stratifying, there would be far fewer multiple samples taken than there are now. In practice, it is not uncommon to have a first stage area sample of, say, census tracts, followed by a second stage sample of blocks, and completed with a systematic sample of households within each block. These stages would not be necessary if a complete listing of households were available.
Example
AC Nielsen’s Multistage Sampling Procedure to select its People Meter Panel
The first stage involves the selection of counties using a stratified random sample based on population. Next within the selected counties there is a random selection of blocks or enumeration districts. These blocks then go through a process called prelisting. A trained field representative visits the selected blocks and creates a list of all the individual hosing units. This list is then returned to the home office where it is checked for internal consistency and external agreement with other data. Finally, individual household units are randomly selected from each block.
The number of stages involved in the sampling method is partially a function of the number of sampling frame available. If a perfect frame were always available complete with all the associated information one might want for purposes of clustering and / or stratifying, there would be far fewer multiple samples taken than there are now. In practice, it is not uncommon to have a first stage area sample of, say, census tracts, followed by a second stage sample of blocks, and completed with a systematic sample of households within each block. These stages would not be necessary if a complete listing of households were available.
Example
AC Nielsen’s Multistage Sampling Procedure to select its People Meter Panel
The first stage involves the selection of counties using a stratified random sample based on population. Next within the selected counties there is a random selection of blocks or enumeration districts. These blocks then go through a process called prelisting. A trained field representative visits the selected blocks and creates a list of all the individual hosing units. This list is then returned to the home office where it is checked for internal consistency and external agreement with other data. Finally, individual household units are randomly selected from each block.