iSixSigma

Chi Square – actual higher than expected in results

Six Sigma – iSixSigma Forums Old Forums General Chi Square – actual higher than expected in results

Viewing 3 posts - 1 through 3 (of 3 total)
  • Author
    Posts
  • #46962

    Tierradentro
    Participant

     I ran the test below and am not sure how to interpret the result based on the fact that the actual cell counts are higher than the expected cell counts, as called out by the warnings at the bottom of the results.
    What is the risk when the actual is higer than the expected?

    •Chi-Square Test: Yes, No

    •Expected counts are printed below observed counts
    •Chi-Square contributions are printed below expected counts

    •          Yes      No  Total
    •    1     131       5    136
    •       123.98   12.02
    •        0.398   4.102

    •    2      29       5     34
    •        30.99    3.01
    •        0.128   1.324

    •    3       5       6     11
    •        10.03    0.97
    •        2.521  25.995

    •Total     165      16    181

    •Chi-Sq = 34.467, DF = 2
    •WARNING: 1 cells with expected counts less than 1. Chi-Square approximation
    •     probably invalid.
    •2 cells with expected counts less than 5.

    0
    #155978

    clb1
    Participant

      What the warning is telling you is that your data is violating the requirements of the Chi-Square test.  Under these circumstances you need to use something like Fisher’s Exact test in its place.

    0
    #155985

    Chi square alert
    Participant

    The first problem is that more than 2 cells out of 6, i.e. 33% of your cells have counts of less than 5. A rule of thumb is to have no more than 25% of the cells with counts of less than 5. This in and by itself raises a red flag. A second red flag is the expected count of less than 1.
    One way to proceed is to collapse your groups 2 and 3 and compare the collapsed groups 2 and 3 against group 1. Another way to proceed is to ignore the red flag if you can explain why you have such a difference in proportions in group 3 (5 vs. 6) as opposed to group 2 (29 vs. 5) and group 1 (131 vs. 5).

    0
Viewing 3 posts - 1 through 3 (of 3 total)

The forum ‘General’ is closed to new topics and replies.