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Graphical Correlation between Discrete X,Y

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  • May 13, 2003 at 3:53 pm #32228

    Kannan
    ★ 10 Years ★
    Participant

    Folks
    I have a case of a discrete X and a discrete Y I am interested in representing graphically correlationships. For example Salesmen (5) against Product Source (5 Warehouses). I have already used pivot tables and stackup histograms…but want a better graphical representation. Any suggestions?

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    May 13, 2003 at 5:18 pm #85847

    Ed VanHaute
    ★ 20 Years ★
    Participant

    If there is a relationship between the salesmen and the warehouses, you can use a dot plot with a regression equation included. I am guessing, however, that the salesmen and the warehouses are both X’s, and you have yet to identify the Y. When you do, use a matrix plot, multi-vari analysis, and/or a multiple regression analysis toshow the relationship between your inputs and outputs

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    May 14, 2003 at 5:21 am #85860

    Kannan
    ★ 10 Years ★
    Participant

    Thanks for your response. I do know the Y and the Y is Delivery Time. I agree with you on both being Xs but this is only to establish a relationship. Also just for you to know the salesman as per a moods median test (non-normal data) is not a critical X. I am still not clear of using a regression equation for discrete Xs.

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    May 14, 2003 at 1:29 pm #85874

    Zilgo
    ★ 20 Years ★
    Member

    You could run a correlation/covariance analysis to see whether or not your Xs are correlated.  A scatterplot of each X versus another will show that if you need it graphically.
    As far as running a regression analysis on discrete X I am going to assume that you really have multiple level categorical data which means you need to run a logistic regression.  If your data has order to it, such as a Likert scale you should use Ordinal Logistic Regression.  If Salesman A could swich places with Salesman B, ie call A B and call B A, you should use nominal logistic regression.  What the correlation analysis will tell you is which two level factors need to be included when you input the model.  What it won’t tell you is which higher order interactions (three and four way) need to be included. 

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    May 29, 2003 at 5:42 am #86454

    Swaggerty
    ★ 10 Years ★
    Participant

    Here’s a simple graph:  square the correlation to get the shared variance between X & Y.  Multiply by 100 to get a percentage.  Plot the percentages in a bar chart and call it “Leverage”.  E.g., this is what salesman X needs to leverage. 

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    May 29, 2003 at 2:59 pm #86472

    Mike P
    ★ 20 Years ★
    Participant

    Use a radar chart (aka spider chart, star plot).  The warehouses will be on the outside edge of the chart, with each as one edge of a pentagon.  Results for each of the five salesmen at each warehouse will be plotted on the inside of the chart with their results color-coded by salesman and the dot of each salesman at each warehouse connected.
    The result is a single, data-rich graph that will show:

    how each salesman performed at each warehouse
    how each salesman performed relative to each of the other salesmen at each warehouse
    the overall ranking of the salesmen (which is the total area of the graph enclosed by their connected points).
    Here is additional information:
    http://www.itl.nist.gov/div898/handbook/eda/section3/starplot.htm
    http://relish.concordia.ca/Quality/tools/23radar.pdf

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    May 29, 2003 at 11:00 pm #86491

    Jonathon
    ★ 10 Years ★
    Participant

    You mention pivot tables, but have you tried a pivot chart? They are pretty powerful, especially if you create a dual-axis chart. That is, the chart holds an X1 and X2 as variables, and displays “towers” for each X1-X2 comnbination. It’s pretty cool stuff, but you need Office 2000 or later.

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    May 30, 2003 at 11:59 am #86504

    John Noguera
    ★ 20 Years ★
    Participant

    Hi Jonathon!
    How’s the book coming along?
    I wanted to mention that SigmaXL creates pivot charts for Excel ’97.
    Also, I wanted to mention that SAS JMP has a similar powerful tool for Discrete X and Discret Y that they call Mosaic Plots.

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