Answer to Question 1
ANS: B
Four sampling designs have been developed to achieve probability sampling: simple random sampling, stratified random sampling, cluster sampling, and systematic sampling.
Answer to Question 2
ANS: C
Systematic variation, or systematic bias, is a consequence of selecting subjects whose measurement values are different, or vary, in some specific way from the population. Because the subjects have something in common, their values tend to be similar to those of others in the sample but different in some way from those of the population as a whole. These values do not vary randomly around the population mean. Most of the variation from the mean is in the same direction; it is systematic. All the values in the sample may tend to be higher or lower than the population's mean. Random variation is the expected difference in values that occurs when one examines different subjects from the same sample. If the mean is used to describe the sample, the values of individuals in that sample will not all be exactly the same as the sample mean. Individual subjects' values vary from the value of the sample mean. The difference is random because the value of each subject is likely to vary in a different direction.
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