järjestysotanta

Järjestysotanta, also known as systematic sampling, is a probability sampling method where elements are selected from an ordered list at regular intervals. The process begins by determining a starting point within the list and then selecting every k-th element, where k is the sampling interval. The sampling interval is calculated by dividing the total population size (N) by the desired sample size (n), so k = N/n. For example, if a researcher wants to select 100 people from a list of 1000, the sampling interval would be 10 (1000/100). The researcher would then randomly select a starting number between 1 and 10, and select every 10th person thereafter.

This method is often simpler to implement than simple random sampling, especially when dealing with large populations. It can also ensure that the sample is spread evenly throughout the population, which can be beneficial if there are periodic variations in the population. However, a potential drawback is that if there is a hidden pattern or periodicity in the sampling frame that coincides with the sampling interval, the sample may become biased. For instance, if every 10th person on a list works in a specific department, and the sampling interval is also 10, the sample might over-represent or under-represent that department. Therefore, it is crucial to ensure that the sampling frame is random or at least free from such cyclical patterns before employing järjestysotanta.