You are concerned about the quality of parts that you are receiving from your supplier. Consequently, you decide to take 25 batches of samples (where each sample consists of 50 units) and to do 100% inspection on these samples. The results are summarized below.

This forms the basis for the initial analysis. Next, you collect information about 20 recent orders that you have received from your supplier in the last month. By the way, it is important to note that your supplier is aware that your firm is concerned about the quality of its parts. These are summarized below:
Sample Data – June 13
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a) Given the information in this problem, calculate the , UCL, and LCL from the base line data. Plot these as an Np control attribute chart.
b) Plot the data from the recent samples using the Np chart derived in (a). What concerns, if any, does this analysis reveal? What management actions would you recommend and why?
c) You receive a telephone call from your supplier informing you that they (the supplier) have significantly changed the production process for your orders at their facility? How would this affect the previous analysis (Np control attribute chart)?

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Batch number Defectives Sample size (n=50) 50 16 Totals 125 Sample Number Sample size Number of Defects 16