8. Random numbers can be used to select a sample only when each item in the population.
A. Can be assigned to a specific stratum.
B. Is independent of outside influence.
C. Can be identified with a unique number.
D. Is expected to be within plus or minus three standard deviations of the population mean.
ANSWER (C) is correct.
REQUIRED: The requirement for use of random numbers in sample selection.
DISCUSSION: A random sample is one in which every item in the population has an equal and nonzero chance of being selected and that selection is not influenced by whether any other item is selected.
Answer (A) is incorrect. Random-number sampling applies to both simple and stratified sampling.
Answer (B) is incorrect. No such requirement exists.
Answer (D) is incorrect. By definition, there are a few population items outside plus or minus three standard deviations from the population mean.