sampling methods

define target pop

group of ppl the researcher is studying

define sample

sample of pp from target pop

define bias

its difficult to select group of pp that perfectly reflect target pop

random sampling

putting names of members of target pop into hat so that every member has equal chance of being chosen

whats a strength of random sampling

• no bias

• every person in target pop has equal chance of being chosen - researcher has no say

• sample more representative

whats a weakness of random sampling

• time consuming and lots of effort needed

• obtain list of all members of target pop & select randomly

• effort may not be worth it

opportunity sampling

selecting ppl who are available at time study takes place & match criteria

whats a strength of opportunity sampling

• easy, quick & cheap to carry out

• choose ppl who are nearby

• less expensive method

whats a weakness of opportunity sampling

• unrepresentative sample

• sample drawn from one area

• reduces results generalisability

systematic sampling

selecting every nth person from a list of all ppl in target pop

whats a strength of systematic sampling

• avoids researcher bias

• no say over who’s selected

• more representative

whats a weakness of systematic sampling

• bias

• sample one particular group of ppl

• decreases representativeness

stratified sampling

selecting pp in proportion to their frequency in target pop

what a strength of stratified sampling

• most representative

• all subgroups represented in proportion to numbers in target pop

• increases representativeness

whats a weakness of stratifies sampling

• time consuming

• take time to identify proportions of subgroups & than recruit pp

• discourages researchers