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Sample Size Question– Category Data

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  • #24139

    Baker
    Participant

    Hello,
    I am working on a situation where I have a number of FAX documents that I receive.  I need to categorize a portion of these FAX documents and determine what “buckets” they fall into for a Pareto analysis.  I have a small population of around 5000-6000 documents and I want to sample this.  How do I determine if I have an adequate sample size in my subset to assume safely that my frequency per “bucket” in the sample matches the population?
    Thanks,
    Jason

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    #57791

    GB
    Participant

    You might consider a small run, or fractional-factorial DOE. Personally, I’d baseline and affinitize your faxes by whatever category is important to you, or your Customer. It could be by Sender, or by affected product/service, or even by time/date stamp. If you have a spreadsheet and the data going back a year, try slicing and dicing by types within 1 month buckets and see what you see.

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    #57799

    Layla K
    Participant

    Hi Jason,
    If your faxes are time stamped, then I think you can take a sample by date.  Depending on the length of time you collected these faxes ( for example, over a month, year, week, few days, etc.).  You could use random systemic sampling (e.g. sample every third day) and over time you should have a representative sample.  If you know of certain behaviours, such as more faxes on Mondays than on Fridays, that could help you decide on your sampling pattern.
    It is suggested to do two sets of samples in this manner, apply your tests on each group – if they are vastly different, you should re-think your samples. But if tests show the groups are similar, then you have a safer set of results that are based upon the true population.
    Hope that helps!

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