Zvalue for 98% confidence level = 2.33 Therefore, control limits for a Chart wit

Question

Zvalue for 98% confidence level = 2.33

Therefore, control limits for a Chart with above Z values

Upper control limit = UCL = Cbar + 2.33 x Square root ( Cbar)

Lower Control Limit = LCL =Minimum ( 0, ( Cbar – 2.33 x Square root ( Cbar))

From the given data,

Cbar = average number of irregularities

          = ( 2 + 4 +7 + 3 +3 + 6 + 5 + 2 + 3 + 4 ) /10

         = 39/10

           = 3.9

Square root ( Cbar) = Square root ( 3.9) = 1.974

Therefore,

UCL = Cbar + 2.33 x square root ( Cbar ) = 3.9 + 2.33 x 1.974 = 3.9 + 4.6 = 8.5

LCL = Minimum ( 0 , ( 3.9 – 2.33 x 1.974)) = Minimum ( 0, - 0.7) = 0

Thus control Limits for Cbar chart is between 0 to 8.5

It is to be noted that all the data on irregularities are within this range of 0 to 8.5. Therefore, it can be said that the process is under control

THE PROCESS IS UNDER CONTROL

Explanation / Answer

5. A car manufacturer buys brakes from a supplier. The following data was provided by the supplier for the car manufacturer to set up a control chart to manage the irregularities. Develop a c-chart fr 98% confidence. Based on the plotted data points, what comments can you make? (20 points) Irregularities 2

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