Random sample

"A probability sample in which people are selected on a totally random, unbiased basis. This can be accomplished by assigning a number to everyone in a community and then letting a computer or hand calculator generate a series of random numbers. If a 10% sample is needed, then the first 10% of the random numbers will indicate who will be the focus of the research. This sampling approach is reasonable for ethnographic research only when there does not seem to be much difference between the people in the population. Since this is rarely the case, random sampling is not often used for ethnographic research". http://anthro.palomar.edu/tutorials/cglossary.htm

(sometimes used in twitter research)