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Thread: Does this graph shows a normal distribution ?

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    Does this graph shows a normal distribution ?




    Hello,

    I am a newbie in Biostatistics field... I would be so thankful if you tell me if below chart has a normal distribution or not and why ?

    Chart title : The distribution of the weight of our donor population

    Thank you very much

    Attached Images  

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    Re: Does this graph shows a normal distribution ?

    It looks near normal. You can also look at the Q-Q plot (where you want data to resemble a 45 degree line) and there are statistical tests for examining data normality.

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    Re: Does this graph shows a normal distribution ?

    Quote Originally Posted by hlsmith View Post
    It looks near normal. You can also look at the Q-Q plot (where you want data to resemble a 45 degree line) and there are statistical tests for examining data normality.
    Thank you very much...

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    Re: Does this graph shows a normal distribution ?

    Hello!
    You can use Shapiro-Wilk test for normality (H0: distribution is normal). I think that is more useful then visual analysis of graph.

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    Re: Does this graph shows a normal distribution ?


    Well, as Aregel mentioned there are tests for normality. However these tests can have limitations, and have the ability to reject the null hypothesis of normality with small departures from the normal distribution when sample sizes increase. I personally feel there is a bigger push to use graphs to get past those types of limitations for tests and to better tackle the end use of data. If the assumption of normality in the proposed analytics is not overly stringent, say as in the t-test with larger samples sizes, then interpreting histograms and Q-Q plots may be good approach. Though other options such as tests exist. Though we must remember either approach could be construed as arbitrary at times (graphs visually interpreted or selected levels of significance used in tests).
    Last edited by hlsmith; 12-10-2015 at 11:34 AM. Reason: typo
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