A call center supervisor inspects the quality of 50 customer service calls per shift for 10 shifts. The number of calls with service issues in each shift is shown below. Shift # Defective Fraction Defective Shift # Defective Fraction Defective 1 3 0.06 6 3 0.06 2 2 0.04 7 2 0.04 3 5 0.10 8 6 0.12 4 1 0.02 9 1 0.02 5 4 0.08 10 3 0.06 Using z = 3, which of the following correctly states the UCL and LCL for the p-chart?
Read DetailsA company records monthly unit sales and uses a 3-month weighted moving average to forecast demand. The weights are: 3/6 for the most recent month, 2/6 for two months ago, and 1/6 for three months ago. Monthly sales are shown below. Month Sales (units) March 20 April 26 May 32 June 38 Using the weighted moving average with the weights described above, what is the forecast for July?
Read DetailsA quality engineer is monitoring a metal stamping process using both an x̄-chart and an R-chart. After reviewing 8 consecutive samples, she observes the following: x̄-chart: All 8 sample means fall well within the control limits with no pattern. R-chart: The sample ranges show a clear and steady upward trend over the 8 samples. What does this pattern most likely indicate about the process?
Read DetailsA quality engineer collects 5 samples of n = 4 parts each from a CNC drilling process. The results are: Grand mean of sample means (x̄̄) = 15.0 mm Average sample range (R̄) = 1.2 mm From Table S6.1, for sample size n = 4: A₂ = 0.729, D₄ = 2.282, D₃ = 0 What are the UCL and LCL for the x̄-chart?
Read DetailsA production supervisor monitors a packaging line by inspecting 200 items per shift over 10 shifts. The average fraction defective across those 10 shifts is p̄ = 0.05. The supervisor uses z = 3. On Shift 11, the inspector finds 24 defective items out of 200. Is the process in control?
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