Question: Individual Question #2 "Chocolate and Quality"

Your Individual Question:

Set up a control chart for the process standard deviation. Based on your s chart only, indicate whether the process is in control.

Steps:

 Make sure to read about control charts, central line, upper and lower limits in the assigned readings for this week module.

 To monitor the weight of the individual chocolate bars, you took samples of size four every 15 minutes for 20 consecutive time periods. Locate sample data in the "Data" worksheet. The data is organized so that observations for the first sample are located in the first row; observations for the second sample are located in the second row, etc.

 Compute standard deviation for each sample and enter your results into the "STANDARD DEVIATION" column (white box).

 The process has been in control with mean μ = 99.55 grams and standard deviation σ = 1.75 grams (yes, grams, because standard deviation has the same units of measurement as the variable mean). Using this information, compute the central line (CL), upper and lower control limits (UCL and LCL) for the s chart. Use formulas for the CL, UCL, and LCL on p.702 of the textbook and the table 12.3 on p.703.

 Set up s chart for the chocolate bar’s weight. To do that, enter the CL, UCL, and LCL into cells labels " S Chart CL, UCL, and LCL" (orange box). If you followed steps correctly, this will populate the plot " S Chart".

 Alternatively, you can use instructions presented in Chapter 17 of the companion Excel Manua l.

 What can you infer about the process stability based on the s chart?

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