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#### Mayank Trivedi

My query is around stratified random sampling calculation.

In a process i am working with we get 3 work types - Simple, Medium and Complex. Simple volume is 90%, medium 6% and complex 4%.

Our client selects a 5% sample for inspection and accordingly gives us our accuracy scores. But the sample they select does not have volume ratio in the same proportion as the population. In the last 3 months it has been Simple - 20%, medium - 45%, complex - 35%.

__Questions:__1) Is it right to use sample size calculator for each of the work types separately? - 5% for each work type?

2) How can sample size be calculated for stratified data like this?

3) For a simple sample size calculator(discrete or continuous) how does one decide on margin of error? For instance, if my accuracy target is 98% for the process does it mean my margin of error in calculation would be +/-2%?

Regards