Eitodennäköisyysotannan

Eitodennäköisyysotanta, known in English as unequal probability sampling, is a sampling technique where each unit in the population does not have an equal chance of being selected for the sample. This contrasts with simple random sampling, where every unit has an identical probability of inclusion. Unequal probability sampling is employed when certain population units are considered more important or informative than others, or when it is more efficient to survey some units over others.

There are various methods for implementing unequal probability sampling. One common approach is probability proportional to size (PPS) sampling, where the probability of selecting a unit is directly related to a measure of its size. For instance, in a survey of businesses, larger businesses might be given a higher probability of selection than smaller ones. Another method involves systematic sampling with unequal probabilities, where units are selected at regular intervals but the starting point and the interval itself are determined by probabilities.

The primary advantage of unequal probability sampling is its potential for increased efficiency and precision in estimating population parameters, especially when population heterogeneity is significant. By oversampling larger or more important units, researchers can obtain more reliable estimates for those specific segments of the population. However, it also introduces complexity in the sampling design and requires specialized methods for data analysis to account for the unequal probabilities of selection. This ensures that the estimates are unbiased and correctly reflect the population.