SAMPLING
Types of Sampling Methods ◦
Non-Probability Sampling -- Items included are chosen without regard to their probability of occurrence. i. ii. iii. iv.
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Judgment Quota Chunk Convenience
Probability Sampling – Items are chosen based on a known probability. Let N=size of the population and n=desired sample size i.
ii.
With replacement -- Prob. of each item and any round =(1/N) Without replacement -- Prob. of each item =(1/N), 1/(N-1), …1/[N-(n-1)]
Types of Probability Sampling â—Ś Items in the sample are chosen based on known probabilities
Probability Samples
Simple Random
Systematic
Stratified
Cluster
Types of Probability Samples, Con’t ◦ Simple Random Sample
-- Every individual or item from
the frame has an equal chance of being selected. In addition, any selected sample has the same chance of being selected as any other. ◦ Samples obtained from table of random numbers or computer random number generators
Divide frame of N individuals into groups of k individuals: k=N/n. Randomly select one individual from the 1st group. Then Select every kth individual thereafter
◦ Systematic Samples --
Types of Probability Samples, Con’t ◦ Stratified samples -- Divide population into
subgroups (called strata) according to some common characteristic. A simple random sample is selected from each subgroup. Samples from subgroups are combined into one
◦ Cluster Samples -- Population is divided into several “clusters,” each representative of the population. Then, a simple random sample of clusters is selected ◦ All items in the selected clusters can be used, or items can be chosen from a cluster using another probability sampling technique