Presentation on theme: "IENG 350-W01 Statistical Process Control How to use Excel in Statistical Quality Control."— Presentation transcript:
IENG 350-W01 Statistical Process Control How to use Excel in Statistical Quality Control
Introduction Why use Excel for Statistical Analysis? 1.Professional statisticians don’t always have powerful software at their disposal. 2.The accompanying diskette in the back of the textbook is for a limited time and has an unfriendly interface. 3.Resourcefulness. Limited budgets and an available application for all students. 4.Limitless. 1.Don’t need to perform nonlinear regression with a custom loss function for maximum possibility. 2.Customized through VBA, and your own ingenuity.
Shewhart Control Charts Most users can create and format simple charts but many don’t exploit Excel’s capabilities for advanced graphical applications. A basic line chart can easily be turned into a Shewhart control chart quickly. Figure 1. Represents data from a machining operation for the diameter of a metal component.The sample average (n=5) are in column F, and the sample ranges are in column G.
Shewhart Control Charts Control limits and center lines are obtained for this X-bar chart do the following: 1.Compute the grand average (double bar X) of the data by using the paste function button (f of x). Type the following into cell F27: = AVERAGE(F2:F26). 2.Compute the average range by copying the formula from F27 to G27. 3.In cell I2: type “= $F$27”. Note the use of absolute references, denoted by the dollar signs.(an absolute address means the contents of a cell are used in a formula, even though it is copied to other cells.) 4.To calculate the upper and lower control limits for a x-bar chart, see table d in text.
5.Use the table d worksheet enclosed in excel file. The sample size is 5, thus A 2 = 0.577. In cell H2, type “ = I2+0.577*$G$27”. 6.For the LCL, in cell J2 type “ = I2- 0.577*$G$27”. 7.All formulas are entered. Copy cells H2:J2 to cells H3:J26 to get control limits and a center line.
8.To get an x-bar chart of the data, highlight cells F1:F26. 9.For noncontiguous cells use the control Key to select cells H1:J26. 10.Select “Insert” from the pulldown menu, then “Chart”.
11.You will create a line chart, choose the first of five in the chart sub-type category. Then click “Next”.
The columns, H,I, and J will display horizontal lines that represent the UCL, Center Line, and LCL. All that is needed is to format the chart after placing within the existing worksheet or on a new worksheet.
To the left is the chart after editing. Right click on the background of chart and select “Format Chart Area” to eliminate the grey background and the border around the chart.
Right click on Lines and select “Format Data Series” and the dialogue box in the lower portion of this slide will appear to enable you to change: UCL and LCL to bold dashed lines with no markers.Change the center line to a lighter solid line with no markers. Change the x-bar data series to a bold solid line with large markers. Edit the lables, fonts, axes,headers, margins, etc.