Create a box plot of the delivery time of two suppliers

Create a box plot of the delivery time of two suppliers

Problem Statement

The attachment shows the delivery time of two suppliers, A and B. The response variable is in the Data column, and the categorical variable (supplier name) is in the group column. Create the box plot showing the delivery time of suppliers A and B and interpret the results.

How to perform analysis

Step 1: Open Sigma Magic
  1. Click on the Sigma Magic button on the Excel toolbar.
  2. Click on the New button to create a new project.
Step 2: Data Preparation
  1. Open the Supplier Data.xlsx attachment
  2. Select the data and convert it to table format by clicking on Ctrl-T


Step 3: Add the box plot template
  1. Click on the Tool Wizard to add the analysis template.
  2. Click on Graph and then Box Plot.
 A new Box Plot worksheet will be added to your workbook, and the following dialog box will be opened. 

Step 4: Specify the analysis options.
The analysis setup dialog box should automatically be opened. Click on the Setup tab on the right.  Accept the default values.



Next, click on the Data tab and specify the data. Drag and drop the Table 1 Data to the Analysis Variables and Table 1 Group to the Categorical Variables.


    Click on the Charts tab to specify any chart options. You can select the following items, but in our example, we will accept the default values.

     Labels:

    • Add a title for the chart.
    • Label the X-axis and Y-axis appropriately.

    Appearance:

    • Adjust colors, font sizes, or other visual elements as needed.
    Enable/disable gridlines or background shading.
    Finally, click the Verify
     tab to ensure all the inputs are okay and shown in a green checkmark.



    Click on the OK button to generate analysis results. The following figure shows an example output screen.



    How to interpret results

    The following conclusions can be drawn from this analysis.
    1. Supplier B has a higher delivery time compared to Supplier A.                                                       
    2. The variation between the two suppliers is similar.                                                          
    3. None of the suppliers have any outliers in the data set.
    4. Median Delivery Time:
      1. Supplier B's median delivery time is 36. Therefore, 50% of delivery from Supplier B occurs within 36 hours;
      2. thus, they take longer time as compared to Supplier A
    5. Distribution of data:
      1. Range 32(Minimum) – 39 (Maximum)
      2. IQR is 35 - 37; this states that 50% of deliveries occur within that range.
    6. Variability: The standard deviation is 2.14; thus, the spread is somewhat greater than Supplier A's.
    7. Outliers: No outliers exist in Supplier B's data.


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