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Control Charts

You have taken data from a production process in order to develop an Xbar control chart. You have 25 samples of data with 5 parts measured in each sample to get the Xbar. Use this data shown in the table.

Sample Xbar

1 2.12

2 2.22

3 1.98

4 2.24

5 1.97

6 1.99

7 2.13

8 2.11

9 2.03

10 1.96

11 1.92

12 2.01

13 2.03

14 2.14

15 1.95

16 2.20

17 1.88

18 1.82

19 2.19

20 2.16

21 2.14

22 1.97

23 1.95

24 2.10

25 2.03

1. First plot the data using Excel.

2. Then determine the UCL and LCL. Do any of the data points need to be thrown out? If so, then recalculate the UCL and LCL.

3. Then you begin to plot results on this chart. Here are the next 6 samples of data (sample size = 5).

Sample Xbar
1 2.24
2 2.22
3 1.95
4 2.06
5 1.99
6 2.05

Plot these on the control chart.

4. Is the process in control?

Attachments

Solution Preview

1. The plotted data is on the first tab of the Excel sheet.

2. With the information given nothing needs to be thrown out if you use 3-sigma as your only limit. However, some people would argue that two of three consecutive points outside the 2-s ...

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