Systematic sampling
Systematic sampling is the selection of every kth element from a sampling frame, where k, the sampling interval, is calculated as:
- k = Number in population / Number in sample
Using this procedure each element in the population has a known and equal probability of selection. This makes systematic sampling functionally similar to simple random sampling. It is however, much more effecient and much less expensive to do.
The researcher must ensure that the chosen sampling interval does not hide a pattern. Any pattern would threaten randomness. A random starting point must also be selected.