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Chi Square Test

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  • #35477

    boettler
    Member

    Can you help, currently i am having great difficulty in understanding the Chi Square test, could somebody send me some examples of how to use a Chi Square test and also how to intepret the results.
    Your help and assistance is very much appreciated, and thank you in anticipation.
     

    0
    #99943

    boettler
    Member

    Please find attached the failure rate for 5 vehicle lines vs cause for rejection.
    I have been ask to complete a Chi Square test on this data, and i am very unsure about how to complete this.

    Cause for Rejection

    Vehicle Type
    Split Tyre
    Seat Bolt
    Flat Tyre
    Bolt in Tread
    Damage / Worn
    Damaged Rim
    Damaged Wheel
    Puncture
    Damaged Side Wall
    Scratched Wheel
    Cut On Side Wall
     
    Total

    A
    1
    4
    1
    13
    0
    1
    5
    4
    0
    4
    1
     
    34

    B
    0
    0
    0
    0
    2
    0
    3
    3
    0
    3
    0
     
    11

    C
    0
    0
    0
    0
    0
    1
    0
    0
    0
    0
    0
     
    1

    D
    0
    0
    0
    12
    0
    0
    1
    10
    3
    0
    0
     
    26

    E
    0
    0
    0
    0
    0
    0
    1
    6
    0
    0
    0
     
    7

    Total
    1
    4
    1
    25
    2
    2
    10
    23
    3
    7
    1

    79
     
    Could somebody send me some details of how to complete the test. i am looking for the following answers for
    a) Do the vehicle types differ with regard to the proportions of failures within each category,
    b) Does the distribution of rejects differ from vehicle o vehicle.
    Regards
    Rob
     
     
     

    0
    #99981

    fernando
    Participant

    I suggest you this link:
    http://faculty.vassar.edu/lowry/webtext.html
    It’s been very useful to me to clarify some concepts. Every subject is explained starting from an example
    You can also download the PDF version
    Fernando

    0
    #100187

    Scott
    Member

    Rob:
    You have an interesting problem that you have been working on.  I am surprised that you have not received a greater response.
    Here are three comments that might stimulate additional thoughts. 
    1. It appears that the sample size is relatively small to draw strong conculsions.  For example, for split trye chi-square = 4. With df=4, and chi-square = 9.488 at the 5% confidence level, there is no statistical difference between vechicle types.  In other words, you can not reject the null hypothesis (Ho: cause A=B=C=D=E).
    2. There is a real danger when statistics is applied to this problem.  A simple statement to management that there is no statistical difference between the vechicle types for split trye could lead to a belief that there is no need to re-visit this question with a large sample size
    3. Chi-square = 47.76 for the totals — statistically significant.  The data clearly shows that some vechile types are worse than others.  In the case of vechicle type B and E, what did you do to determine if there is a statistical difference between these two vechicle types?  
    I would be interested in finding out more about your final analysis.

    0
    #100190

    Savage
    Participant

    A great way to set this up is to use a Pivot Table in Excel, then run the Chi-Square function.  I’ll set it up and give it a try.
     

    0
    #103558

    Sanjay Kumar
    Member

    Dear ,
     
    Please mail me that table if you can.
     
    Regards,
     
    Sanjay Verma

    0
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