sampling Flashcards
what is opportunity sampling
people who are available at the time are selected
2 strengths of opportunity sampling
time efficient
saves money and its easy, as the population doesnt need to be divided into different strata
limitations of opportunity sampling (2)
-unrepresentative of whole population-lacks generalisability as it is drawn from a very specific area
-researcher bias- theyre controlling whos selected
what is random sampling
everyone in the population has equal chances of selection
eg. random number generator
2 strengths of random sampling
-no researcher bias
-confounding/extraneous variables should be equally divided between the 2 groups- increased internal validity
limitations of random sampling
time consuming - must have a sampling frame of entire population. contacting people takes time
what is systematic sampling
every nth number is selected from sampling frame
2 strengths of systematic sampling
-no researcher bias
-representative of whole population
what is volunteer sampling
self selection of participants
strength of volunteer sampling
more likely to cooperate as theyre more engaged
limitation of volunteer sampling
volunteer bias- will attract a certain profile of people who are more likely to ‘please’ the researcher- demand characteristics
what is stratified sampling+ how to select a sample (3 steps)
-sample reflects proportions of strata in a population
1. identify the different strata
2. sample needs to be representative, so proportions must be worked out
3. p’s that make up each strata are randomly selected
2 strengths of stratified sampling
no researcher bias
is representative data due to proportional strata
2 limitations of stratified sampling
-time consuming to identify strata and complete representation of population isnt possible
-identified strata cant reflect all the differences between people of the wider population
2 limitations of systematic sampling
-time consuming
-participants may refuse to take part, resulting in a volunteer sample
