Inter State Moving and Storage Company is setting up a control chart to monitor

Question

Inter State Moving and Storage Company is setting up a control chart to monitor the proportion of residential moves that result in witten complaints due to late delivery, lost items, or damaged tems. A sample of 55 moves is selected for each of the last 12 months The number of witen complaints in each sample is 7,6,6,7,4, 7,10, 5,6,4, 8, and 15 Click here for the Excel Data File a. Insert the mean proportion defective, UCL, and LCL (Round your intermediate calculations and final answers to 2 decimal Mean proportion defective c. Does it appear that the number of complaints is out of control for any of the months Yes O No C Prev 11 of 13 Next here to DFGHJK

Explanation / Answer

mean proportion defective =total defective /ttoal sampled =85/(12*55)=0.13

as std error =(p*(1-p)/n)1/2 where n=55

=0.045

hence LCL =sample proportion -3*std error =0.00

UCL = sample proportion +3*std error =0.27 ( please try 0.26 if this does not work due to rounding error)

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