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Thread: Appropriate statistics where dataset contains only positive cases?

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    Appropriate statistics where dataset contains only positive cases?




    Sorry if this sounds confusing or uses the wrong terminology, I'll do my best to explain.

    I have a data set of approximately 100 records, where every one of those 100 records is of a person suffering a particular illness (the illness is the area of study).

    The variables within the data are of factors that I want to investigate as to whether they have an effect. Examples of these are Male/Female, age, and then some more specific details.

    I'm unsure what I can actually do with this though, statistically speaking. I know I can compare how many males versus females get this illness. I can look at the age distribution. I can look at the relative frequencies for the other variables in isolation. But all these seem to be telling me are how these factors are distributed within the "ill" population, I have no idea what they are in the "healthy" population because that isn't recorded.

    Am I right in thinking that there isn't much more that can be done other than that?

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    Re: Appropriate statistics where dataset contains only positive cases?

    Correct, with only cases you are limited.
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    Re: Appropriate statistics where dataset contains only positive cases?

    You could compare the percentage of these groups who have the illness to the preportion in the general population. For example you might note that (I am making this up of course) that 51 percent of the US population is males, but 60 percent of the people who get illnesses are male. This proves nothing, statistically or substantively, but suggests patterns for future analysis.
    "Very few theories have been abandoned because they were found to be invalid on the basis of empirical evidence...." Spanos, 1995

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    Re: Appropriate statistics where dataset contains only positive cases?

    I was thinking what noetsi said -- incorporate some background info on the population (hospital, city, state, ... whatever is the "population"), and be sure any conclusions/discussion you make off this analysis is made in the correct context, i.e. limited sample on 100 ill people only with background/denominator data obtained seperately. Questions that might arise include: are these 100 cases really representative of cases from the population; are these cases truly from the population from which the background info was obtained; are these cases a random sample. And you really can't make statements about "likelihood" "odds" or "probability" of becoming a case. I agree with you that anything you come up with will really just be descriptive information.
    The mathematical explanation of a statistical procedure is really just pseudo-code, which we can make operational by translating it into real computer code. --B. Klemens

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    Re: Appropriate statistics where dataset contains only positive cases?


    Thank you very much to everyone who replied. It's reassuring to know that I'm thinking along the correct lines.

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