Stensil Fertilizer and Chemical Co. Inorganic Fertilizer Testing

Read the second case (Stensil) description below (also found in the Excel file, second tab).
Watch the second video in this module which explains how to build an SPC chart in Excel (the video must be
watched in its entirety to get full credit).
You must also submit a Word document containing a memo to Bill Evans, Quality Control Manager for Stensil.
Case 2 Description
Stensil Fertilizer and Chemical Company produces both organic and inorganic fertilizers. Organic fertilizers are
generally safe, but inorganic fertilizers are carefully monitored by the EPA due to the presence of hazardous
waste materials (hazmat). Most bags contain some hazardous content, but theoretically there should be none.
The EPA allowable specification is 90 parts per million (PPM). The quality control department at Stensil feels
that there is no problem with hazardous material content, which has been averaging just over 50 PPM. The
production department estimates that a substantial investment would be required to lower the amount of this
contaminant. These two departments, after consulting with the marketing department and the EPA, suggest
that a control chart be set up to monitor hazmat content. Five samples will be tested per day and plotted as one
point on the chart. Use the data in Table 1 to set up the control limits. Then, after the limits are in place for this
process, use Table 2 to determine whether or not the process remains in control for the week of September 6—
The Excel file includes a second tab for the Stensil Fertilizer Case (Case 2). This is the data you need for the
problem. Build an appropriate SPC X-bar Chart and R-chart for the Table 1 data on this tab of the Excel
Then, test to determine whether the Table 2 data indicates the process is under control for that period. Show
your work for this part in the same Excel worksheet and submit it.

Sample Solution