Delta Plastics Inc Case Study

Prepare a 3-sigma control chart for both production processes.

The control data is based on a chart showing the type of defect as well as the number of defects for one month, a total of 20 days. The average number of defects for the standard material is 1.93 and the range is 2.6. The control limit is 2.41, the upper control limit is 3.28 and the lower control limit is .571. The average number of defects for the new material is 2.44 and the range is 4.55. The control limit is 2.41, upper control limit is 4.14 and the lower control limit is -1.73.

Discuss whether or not both processes are in control and what conclusion may be drawn.

A P-chart was used to determine the above answers. P-charts are used to measure the defective proportion in a given sample (Reid and Sanders, 2010). A P-chart method describes products as “good” or “bad” because this method is not a quick fix quality management system ( After developing control limits, a P-chart will be able to understand the overall proportion of defects ( Both processes seem to be in control. At a glance, the figures and the defects of the two materials seem to conclude that the new material is out of place.

The problem is to determine whether or not both of these processes are in or out of control. If you were to look at each process on its own, one could say that the process looks very out of control. When you look at the process of, for example, the cracks in the new material compared to the cracks in the standard material, you find there are more process errors in the new “super plastic”. In the one month these two processes were observed there were 93 cracks in the “super plastic” compared to the 41 cracks in the standard material. When all data is compared, the defects with the “super plastic” nearly double that of the standard material. In the final analysis, it can be concluded that the company finds itself at a crossroads without a sense of direction. Delta Plastics, Inc. wanted to position the company in the market at before any of their competitors. Delta Plastic would have to begin all over again with the research on the new material or become happy with the standard version of plastic and face the competition head-on.

Discuss whether or not both materials are equally subject to defects.

Both products are equally subject to defects. For example, the average number of total defects on containers made out of standard material, considering the 20 days of observation, is 9.65, while the average for containers made with the new material is 12.05. These figures are calculated by adding all of the defects for every day and dividing that total by 20 (the total number of observations). The following data shows the average defects for each category for both the standard material and the “super plastic”:



I applied through a recruiter. The process took 2+ months. I interviewed at Delta Plastics in January 2014.


A accounting rec. service who reached out to me. The interview process started in early December and didn't end until late January. First I went to the rec. agency and they proceeded to get me a phone interview. Once I passed the phone interview I was called into the CEO to meet and then was given a written math test to show if I can without a computer or calculator solve a written case study and show that I know what a profit margin is and how to manually conclude percents. I was applying for a customer service manager position/sales - The CEO simply spoke about himself told me he had children, wife, and was born in SLC, UT. then he asked me to tell him about me. Then he left and the current manager handed me the paper with the test. They both kept asking if I had questions but didn't really ask me any questions. I felt is was a very strange interview. I have several years experience in management. I told the rec. agency about it, and the next day they told me I wasn't a good fit, told my I dressed badly, and several other inappropriate untrue remarks. I have never been so offended by both organizations. I would never recommend either of them to anyone. I had worn the same outfit I wore for the, and several interviews. I do dress very professional and my family and friends assured me that I do and did dress well and I would have thought if I dressed badly the rec. agency after meeting me would have not pushed me further in the process. I warn you.. this company is STRANGE!

Interview Questions

  • written math test with no calculator - seems they may use green-sheets and not Excel.   Answer Question
Delta Plastics 2015-01-28 14:48 PST

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