Assessing normality/kurtosis/skewness in SEM

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  • #3679

     

    Hi,

     

    When assessing the normality based on the skewness and kurtosis reading in SEM, which value do we actually refers to – the kurtosis value, or the critical ratio value.

     

    Literature indiates that value of 3.0 for skewness and 10 for kurtosis is acceptable (Kline, 2005).

     

    Thanks.

    #3682
    Jeremy Miles
    Participant

    The value.  The value is a descriptor of how far from normality it is.  The critical ratio is used to get the p-value, which depends on the sample. So for a larger sample, the same degreed of skew (and hence the same problem) will have a larger critical ratio (which makes it seem like a worse problem.)

    #3681

    Thanks Jeremy.

    #3680
    diana k
    Participant

    if you want to know about normality, skew is a VERY poor choice

    Kolmogorov – Smirnov, avaialble in most stats packages is much better, or try eyeballing a normal percentile plot, also avialble in eg SPSS.

    or just produce a simple box & whiskers diagram. if its non-normal and skewed then the 75% and 25% will not be equal distance from median, also 90% and 10%. if it is high kurtosis, but symmetric then outliers will show up.

     

    if the reason for non-normality test is to use t-test or ANOVA, then be aware that unequal variance is a wors problem than skew. use unequal variance form of tests

     

    best

     

    Diana

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