Aspects of Cluster Sampling
One version of cluster sampling is area sampling or geographical cluster sampling. Clusters consist of geographical areas. Because a geographically dispersed population can be expensive to survey, greater economy than simple random sampling can be achieved by treating several respondents within a local area as a cluster. It is usually necessary to increase the total sample size to achieve equivalent precision in the estimators, but cost savings may make that feasible.
In some situations, cluster analysis is only appropriate when the clusters are approximately the same size. This can be achieved by combining clusters. If this is not possible, probability proportionate to size sampling is used. In this method, the probability of selecting any cluster varies with the size of the cluster, giving larger clusters a greater probability of selection and smaller clusters a lower probability. However, if clusters are selected with probability proportionate to size, the same number of interviews should be carried out in each sampled cluster so that each unit sampled has the same probability of selection.
Cluster sampling is used to estimate high mortalities in cases such as wars, famines and natural disasters.
Read more about this topic: Cluster Sampling
Famous quotes containing the words aspects of, aspects and/or cluster:
“That anger can be expressed through words and non-destructive activities; that promises are intended to be kept; that cleanliness and good eating habits are aspects of self-esteem; that compassion is an attribute to be prizedall these lessons are ones children can learn far more readily through the living example of their parents than they ever can through formal instruction.”
—Fred Rogers (20th century)
“... of all the aspects of social misery nothing is so heartbreaking as unemployment ...”
—Jane Addams (18601935)
“Next week Reagan will probably announce that American scientists have discovered that the entire U.S. agricultural surplus can be compacted into a giant tomato one thousand miles across, which will be suspended above the Kremlin from a cluster of U.S. satellites flying in geosynchronous orbit. At the first sign of trouble the satellites will drop the tomato on the Kremlin, drowning the fractious Muscovites in ketchup.”
—Alexander Cockburn (b. 1941)