Question

In: Operations Management

Five samples of size 4 were taken from a process. Summary statistics are shown below: Sample...

Five samples of size 4 were taken from a process. Summary statistics are shown below:

Sample Range Mean

1 1.75 10.5

2 2.42 22.3

3 2.75 17.4

4 2.04 20.1

5 2.80 18.9

What is the lower control limit for a range chart?

Solutions

Expert Solution

Solution:
We need to calculate Lower control limit for a range Chart which can be calculated as
LCL range chart = D3*Rbar
Here Subgroup size = 4
No. of sample n = 5
Rbar can be calculated as
Rbar = (Range)/n = (1.75+2.42+2.75+2.04+2.80)/5 = 11.76/5 = 2.352

From D3, D4 and A2 table we found at Subgroup size = 4, D3 = 0
So Lower control limit for range chart = 0*2.352 = 0


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