The first choice is incorrect. C&A; wants to develop process control charts to m

Question

The first choice is incorrect.

C&A; wants to develop process control charts to measure the weight of crates of wood. Data (in pounds) from three samples are: C&A; wants to develop process control charts to measure the weight of crates of wood. Data (in pounds) from three samples are: Which of the following control charts should be used? x-bar chart with UCL=36.2 and LCL=15.8 and range chart with UCL=25.7 and LCL=0 x-bar chart with UCL=33.3 and LCL=18.7 and range chart with UCL=22.8 and LCL=0 x-bar chart with UCL=22.8 and LCL=0 and range chart with UCL=33.3 and LCL=18.7 x-bar chart with UCL=25.7 and LCL=0 and range chart with UCL=36.2 and LCL=15.8 None of the choices.

Explanation / Answer

xbar-bar = 26.00 and Rbar =10 and subgroup size n = 4

CL = 26.00

LCL = xbar-bar - A2Rbar = 26.00 - 0.729 * 10 = 18.7 [ A2 = 0.729 for subgroup size n = 4 ]

UCL = xbar-bar + A2Rbar = 26.00 + 0.729 * 10 = 33.3

so x - bar chart with UCL = 33.3 and LCL = 18.7

Range Chart =

UCL = D4Rbar = 2.282* 10 = 22.8 [ D4= 2.282]

LCL = D3 Rbar = 0 [ D3 = 0]

Option - B is correct.

Sample Crate 1 Crate 2 Crate3 Crate 4 Average R 1 18 38 22 26 26 20 2 26 30 28 20 26 10 3 26 26 26 26 26 0 mean 23.33 31.33 25.33 24.00 Range 8 12 6 6 X(bar - bar) 26 R(bar) 10

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