Cluster sampling
18 important questions on Cluster sampling
What is a cluster sample?
In cluster sampling, the population is divided into subpopulations (clusters) of which you take a random sample - a subset of all possible clusters. From a selected cluster, all elements are included. Cluster sampling can with or without replacement and with equal probabilities (when the clusters are of equal size) or with unequal probabilities (when the clusters are of unequal size).
Why are the variances of cluster sampling estimators usually larger?
What are two designs for cluster sampling?
2. Selecting clusters with probabilities proportional to size.
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What is an advantage of selecting clusters with probabilities proportional to size?
What is two-stage cluster sampling?
What are two advantages of cluster sampling?
2. Cluster sampling can be used when individual selection (SRS) is too expensive (e.g. visiting multiple schools to sample multiple children instead of visiting one school to sample an amount of children).
What are two disadvantages of cluster sampling?
2. Statistical analysis is more complex than for SRS.
Since clusters sampling provides generally less precision than SRS, it is advised to use cluster sampling only in two situations. What two situations?
1. ... it is economically justified (cost savings overcome (or require) loss in precision).
2. ... constructing a complete list-based sampling frame is difficult, expensive or impossible and the target population is located in natural clusters (e.g. regions, schools, city).
What is a consequence of cluster sampling for independence of observations?
What is the sampling fraction for a one-stage cluster sample?
Where m is the number of sampled clusters and M is the population number of clusters.
When is a cluster sample self-weighting?
From the formula for the variance of the mean estimator for cluster sampling it can already be seen that cluster sampling is less efficient than SRS. How?
How is dealt with clusters of unequal size?
What is the inclusion probability (sampling fraction) of a two-stage cluster sample?
Of what two elements consists the formula for the variance of the mean estimator in two-stage sampling without replacement?
Why do clusters that are of unequal size have to be treated different from clusters that are of equal size?
What is meant with the 'cluster effect'?
By what is the precision of the estimator primarily determined when primary units are selected with replacement?
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