Sampling Flashcards
(15 cards)
simple random sampling
each member of the population has an equal chance of being picked. e.g. names in a hat or random number generator
cluster sample
the population is divided into groups (clusters). some of the clusters are selected using simple random sampling. all the members from the selected clusters are sampled.
systematic sample
the population is ordered in a list. the size of the population is divided by the size of the sample required to give the sampling interval. a starting point is randomly chosen and then we skip ahead in step sizes equal to the sampling interval.
stratified sampling
the population is split into groups of the same characteristics (strata). the number of members to be selected is proportional to the size of each strata. those members are then selected using a simple random sample.
quota sample
the population is split into strata (as in stratified sampling). a desired number of members from each strata is decided upon. the interviewer conducts the survey enough times until these desired quotas have been reached.
strengths of simple random sampling
unbiased
quick and easy
not expensive
weaknesses of simple random sampling
not a fair representation of the population
strengths of cluster sampling
quick and easy
less people so more convenient
weaknesses of cluster sampling
can be biased when clusters are made
strengths of systematic sampling
unlikely to be biased
weaknesses of systematic sampling
time consuming
not likely to be representative
strengths of stratified sampling
very representative
weaknesses of stratified sampling
very time consuming
prior knowledge of population is needed
strengths of quota sampling
easier than stratified
weaknesses of quota sampling
can be biased
