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Experience with g-Charts?

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  • #52661

    OldMBB
    Participant

    Not a joke… this is a new SPC thingy to me after 25 years…
    I was referred to a couple publications from Wheeler and Benneyan talking about g-charts as superior in ultra-low defect rates so that it turns it over as “units between failures” (as data points increase = better)… of-course it needs a whole different UCL and LCL calculation…  It also seems to be in STATIT and QIMACRO but not Minitab yet…
    Does anyone have any REAL experiences with this stat — does anyone (that has to be an operational type) see this as worthwhile?
    Thanks

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    #185562

    Dalziel
    Participant

    I’ve seen them used for trending accident statistics in a manufacturing environment – Didn’t use them personally, but the “days between occurances” metric made sense.
    I can’t remember too much about them, as my area’s safety performance was measured more along the lines of a DPMO calculation.
     

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    #185565

    Bower Chiel
    Participant

    Hi OldMBB
    I have no experience of using these charts but are aware of people here in Scotland who have been applying them in Healthcare e.g to hospital acquired infections.  I noticed a paper which might be of interest to you at http://www.bing.com/search?q=geometric+control+charts&FORM=CBPW&first=1 .
    Best Wishes
    Bower Chiel

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    #185566

    Bower Chiel
    Participant

    Hi OldMBB
     
    I should have pasted : –
    http://www.cpqcc.org/documents/165/download
    Apologies
    Bower

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    #185673

    Savage
    Participant

    There are two types of rare event control charts that are gaining attention. If you find that a traditional control chart is not working for you, you may consider using a g-chart or t-chart. The t-chart is similar to the g-chart except the time between a rare event is recorded. I.e. the days (or weeks or …) passed since the last on-the-job injury.
    PQ Systems, the company I work for, has software (CHARTrunner) that creates g-charts and t-charts. I think t-charts are easier to understand, but that is my 2¢.

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