Sampling
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Can someone please explain stratified sampling? I am doing the June 05 PCR Paper for revision and even the answer to the dreaded writing bit is not clear.
I understand that that you select samples from groups - but what groups? The question does not specify that there are groups of employees - what assumptions am I supposed to make in this respect?
I would be grateful if someone could explain this to me.
I understand that that you select samples from groups - but what groups? The question does not specify that there are groups of employees - what assumptions am I supposed to make in this respect?
I would be grateful if someone could explain this to me.
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Re:Sampling
Stratified sampling involves dividing the data into groups, strata means 'layers'. You simply choose a sample from each of the layers (strata) according to their size. The bigger the layer, the bigger sample you choose.
For example, you could be sampling purchase invoices for errors. The layers would be the customers. Say one customer has 10 invoices and the other 3, it is clear you would pick a bigger sample from the one with 10.
I hope that's made it more clear, was struggling with an example to be honest!0