a sub group within a population is identified e.g. age groups, this representative as percentage total of the whole population, participants then selected through opportunity sampling
advantage
more representative than opportunity sampling a there is equal representation of subgroups, a deliberate effort is made to make the sample representative of the target population
disadvantage
it can be time consuming as the sub categories have to be identified and proportions calculated, as it uses opportunity sampling, it still has the weaknesses of this method also
