When is cluster sampling appropriate?
a. Cluster sampling is a good choice when the population has multiple distinct groups that are each likely to be representative of the population as a whole.
b. Cluster sampling is a good choice when the population has multiple distinct groups that are internally homogenous but not representative of the population as a whole.
c. Cluster sampling is useful if the population is not well understood or there are no groups within the population that need to be analyzed individually.
d. Cluster sampling is a useful method when the individuals in the population are generated in a continuous stream, like on an assembly line.