Sampling

Stratified sampling:

Stratified sampling is when you sort data out into groups and randomly sample from each.

For example:

 You have secondary data and you want to see who performs better, males or females. So you would sort out the data into males and female, something like this:

Then to work out how many random samples you are going to pick it thought the formula:

Number of candidates in group (strata) / Total samples * Total number of samples

In this context it would be for females: 555/1199*60

Random sampling:

Then you do random sampling, you can do this in many ways ie: #Ran button on calculator, Utilities (android phone) and Google