Stratified sampling is a method of surveying certain groups of people in proportion to each other. For example imagine you want to survey a year 10 group and a year 11 group. In year 10 there is 100 people and in year 11 there is 200 people and you want to survey 50 people. If you were to enter this data into the stratified sampling calculator it would generate how many people you should survey in proportion to the amount of people in the group. So it would tell you to survey more people in year 11 to year 10
To work out the number of people to survey there is a formula. Total amount of people in a single group / total amount of people from all groups * amount of people to survey. By doing this it will give you the answer but with the stratified sampling calculator you don't have to worry about remembering and calculating the maths where there could be a possible mistake.