PART 3: Conclusions The Operations Manager at Bobcat Manufacturing states they a

Question

PART 3: Conclusions The Operations Manager at Bobcat Manufacturing states they are ready to submit their bid for the project since the control charts are showing that the process is ‘in control’. Do you agree or disagree with this decision? Why? (Consider your answers for Part 1 and Part 2).

Part 1.

Xbar for a sample = sum of 8 sets of data/ 8

Range for sample = Highest value – Smallest value

Thus,

Xbar-bar = Average of Xbar values = Sum of Xbar values / 5 = 8.68

Rbar = Average of Range values = sum of Range values / 5 =2.64

Sample size = n = 8

Following are the relevant values of constants for n = 8 as derived from standard table for Xbar and Range values :

A2 = 0.373

D4 = 1.864

D3= 0.136

Xbar chart :

Upper control Limit ( UCLx ) = Xbar + A2 x Rbar = 8.68 + 0.373 x 2.64 = 8.68 + 0.984 = 9.664

Lower Control Limit ( LCLx) = Xbar – A2 x Rbar = 8.68 – 0.373 x 2.64 = 8.68 – 0.984 = 7.696

Range chart :

Upper control Limit ( UCLr) = D4.rbar = 1.864 x 2.64 = 4.92

Lower control Limit ( LCLr ) = D3.rbar = 0.136 x 2.64 = 0.359

It is to be noted that :

All calculated values of xbar ( for 5 samples ) are within control limit 7.696 - 9.664

All calculated values of rbar ( for 5 samples ) are within control limits 0.359 – 4.92

Therefore, process is fully in control and therefore Bobcat manufacturing continue operation with current process.

Part2.

Explanation / Answer

From the above calculations, we can agree with the conclusions of Bobcat manufacturing and continue operation with the current process.

The process is in control as can be seen from the fact that all the X-bar are within control limit range of 7.696 - 9.664 and all the R-bar values lie within control limits range of 0.359 – 4.92.

If the values were outside the respective ranges then changes would have had to be made to the process. Hence Bobcat manufacturing should submit their bid for the project with confidence.

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