Wednesday, April 16, 2014

Statistical Process Control With VBA

Before returning to graduate school, I worked in a job that required the use of statistical process control (SPC).  SPC requires real-time monitoring of process data and frequent additions to the data set as the process is often ongoing.  While statistical software has been effective for me in analyzing static data sets, it has often been cumbersome for ongoing process data as described.  VBA presents an opportunity to analyze dynamic data with little effort in loading and manipulating the data.

For my internship this summer, I will be working with a contract manufacturer for P&G to reduce scrap in their manufacturing process.  I am certain that I will use statistical process control.  The project that I created will allow me to add data manually, or bring in data from a website or database.  Because I don’t currently have any live manufacturing data, I am pulling real-time trading volume data from Yahoo Finance to be analyzed.

I used a wide variety of VBA concepts in this project to enhance functionality and to broaden my understanding of the concepts.  The program includes user forms, a modified ribbon, arrays and charts generated by VBA.


This program opens and runs automatically at 2 pm every day to retrieve the latest data for analysis.  User forms allow the user to decide whether to run variable control charts (for continuous data) or attributes control charts (for discrete data).  Based on control chart type selection, the user can then select from an array of specific control charts, and create a histogram to check for normality of data.  The charts are then generated based on the user’s selections, and control limits are added to the charts to allow the user to make appropriate decisions regarding the process.

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