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Thread: Which test for significance: Compare counts between two time points [Excel]

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    Which test for significance: Compare counts between two time points [Excel]




    Hello -

    First time poster. Thank you in advance for any advice that you can give.

    I am conducting a simple descriptive analysis of patients who came in for a particular service over a 10-year period. I made the statement to my boss that demand for this service increased by about 450% over time by simply comparing the # of patient who came in during the first 12 mos (N=12) and the # who came in during the last 12 mos (N=67). When I told her this, my boss keenly asked if I *knew* whether this was a difference (significant) or not. I did not actually know for sure.

    Basically, I want to confidently make the statement that demand increased over time but I'm not sure what test to use to check for significance. I have chosen to just compare the count of patients for the first 12 mos and the count of patients for the last 12 mos, with the implicit expectation that the # of patients per year would not change. What test would be best for this simple analysis?

    At first I thought independent, two-tailed t-test. There is one population for the study, but this question is asking about the difference between two groups of diff people: those who came in during the first 12 mos and those who came in during the last 12 mos. But t-test isn't appropriate because I am not using means or
    proportions.

    Then I thought Poisson. But Poisson is really only appropriate for large counts that will conform to the Poisson distribution and these are not large counts. I also thought Chi2 for a min, but this is not categorical data and I don't really know what my expected amounts would be. I suppose I would expect that the # of people coming in
    would be the same during the last year as the first, but that test still doesn't seem like a good fit.

    I have checked the web and old stat texts. I feel like I am missing something really obvious. But I have not found the right test to answer this question: Test for significance comparing two counts between time 1 and time 2.

    Thanks for any help you can offer!

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    Re: Which test for significance: Compare counts between two time points [Excel]

    You can use a ChiČ test with 2 cells and the Null hypothesis
    that the total n=79 patients come from a population with an
    even (50%/50%) distribution across the two years inspected.

    With kind regards

    K.

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    Re: Which test for significance: Compare counts between two time points [Excel]

    Thanks, Karabiner! This worked perfectly and jogged my rusty stat memory. Appreciate your help.

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    Cool Re: Which test for significance: Compare counts between two time points [Excel]


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    Re: Which test for significance: Compare counts between two time points [Excel]

    Hi, i have a doubt that i would like to clarify:

    My question is:

    How i calculate the weighted mean?

    Ps.: see the file attached.

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    Smile Re: Which test for significance: Compare counts between two time points [Excel]


    I sent you an attachement with an question that i want to be solved. And iŽll be available to support you with your doubts.
    Attached Images

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