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
strengths of systematic sampling
no researcher bias, usually 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
