An accountant has to check a sample of invoices. the invoices are divided into 3 groups by value as follows: under 100pounds, 100-500pounds, over 500pounds. Samples are then selected randomly from each group. Which method of sampling is being used?
Answer: stratified sampling
Sir i want to understand why the answer is stratified sampling, because technically no weights or proportion of each category has been mentioned.
Why not multistage sampling? although here it can be argued that there is only one stage.
Obviously they will need to know how many invoices there are in each grouping (or strata) to decide how many to sample from each strata. However how many they will sample is not relevant for the question – it is just the fact that breaking the invoices down into strata and then sampling is what stratified sample is.