sampling techniques Flashcards
what is target population
larger group of people that the sample is taken from
what is a sample
group of people who take part
what is random sampling and how is it carried out
a sample of ppts produced by using a random technique such that every member of the target population being tested has an equal chance of being selected e.g random number generator
strengths of random sampling
unbiased- everyone has an equal chance
eliminates researcher bias
limitations of random sampling
need to have a list of all members of the population and then contact all those selected which may take some time.
might end up with a sample that is not representative e.g same gender
how to carry out random sampling
list all names from target population
number the names
put numbers into random number generator
match number back to the name
what is opportunity sampling
recruit those people who are most convenient or available, e.g people at school or on the street. A sample of ppts by selecting people who are most easily available
strengths of opportunity sampling
easiest method as u use the first ppts u can find so takes less time
limitations of opportunity sampling
biased because its drawn from a smaller part of the population
unrepresentative because your getting it from a small area
what is volunteer sampling
a sample of ppts that relies solely on volunteers to make up the sample. Advertise in a newspaper or noticeboard. (self selected)
strengths of volunteer sampling
gives access to a variety of ppts e.g all ppl who read a particular newspaper which may make the sample more representative and less biased
minimal imput from researcher
limitations of volunteer sampling
volunteer bias as it attracts only a certain type of people
what is systematic sampling
where the researcher chooses every nth member of the target population
strengths of systematic sampling
no researcher bias- not deciding whos chosen
representative
limitations of systematic
time consuming
what is stratified sampling
subgroups within population are identified e.g age group ppts obtained from each of the strata in proportion to occurrence in population
strengths of stratified sampling
most representative technique as it is the right proportion.
limitations of stratified sampling
time consuming
how to carry out stratified sampling
step 1- identify subgroups/strata
step 2- calculate proportion of people in target population for each subgroup
step 3- calculate proportion of people from each subgroup needed in the sample
step 4- the number of ppts in target pop+ use random number generator to generate selected person.
step 5- match number back to name and repeat for each subgroup
