Final answer:
A self-selected sample is one where individuals voluntarily choose to participate, which often leads to a biased and non-representative subset of the population since it does not give every member an equal chance to be included.
Step-by-step explanation:
When a sample group is self-selected, it means the individuals in the group have voluntarily chosen to be part of the study or survey, rather than being randomly selected. Self-selected samples often arise from sources like internet surveys where individuals decide whether they want to participate. Because of this method of selection, self-selected samples are likely to be biased and should be treated as non-representative. Representative samples are designed to reflect the characteristics of the whole population by giving every member an equal chance to be included. Factors such as response bias, selection bias, and sampling errors can severely undermine the accuracy of self-selected samples, leading them to deviate significantly from the general population.
For instance, during the state of the United States in 1936, a sample chosen from magazine subscription lists, automobile registration lists, phone books, and club membership lists was not representative because it systematically excluded significant segments of the population who did not subscribe to magazines, own cars, have telephones, or belong to clubs, which at that time, were considerable in number due to economic disparities. This exemplifies how such samples can lack proper representation of the populace.