statistical sampling 1.1 Flashcards
what is population
the whole set of items that are of interest
what is sample
some subset of the whole population intended to represent the population
what is sampling unit
each individual thing in a population that can be sampled
what is a sampling frame
often sampling units of a population are individually named or numbered to form a list
what is a census
when you collect data from entire population
strength of sample
cheaper
quicker
less data to process
weakness of sample
not accurate
not large enough to represent
small sub groups
strength of census
should give completely accurate results
weakness of census
time consuming
expensive
large volume of data
what is simple random sampling
each item is given a number then random number generator selects the number
strength of simple random sampling
bias free
easy and cheap
each number has equal chances
weakness of simple random sampling
not suitable for large pop
not representative
sampling frame needed
what is stratified sampling
population divided into sub groups same proportion to sample as to pop
strength of stratified sampling
reflects population
guarantees representation
weakness of stratified sampling
population must be in groups
selection within groups
what is systematic sampling
people choose at regular intervals e.g.every 100th
strength of systematic sampling
simple and quick
suitable for large samples
weakness of systematic sampling
sampling frame needed
can be bias
what is quota sampling
population divided into groups then opportunity sampling
strength of quota sampling
can be representative
no sampling fram
quick easy
weakness of quota sampling
bias
must be divided to groups
non response are not recorded
what is opportunity sampling
sample taken from people who are available at the time
strength of opportunity sampling
easy to carry out
inexpensive
weakness of opportunity
not representative
bias
