Question

EPA regulates the level of CO2 emissions. Recently, the EPA began applying an automated control chart methodology to detect undermeasurement of emissions data. The three daily samples of CO2 levels for each of 15 days are shown in the below table.

a. Construct two control charts for the daily average and variation of CO2 levels.

b. Based on the control chart, describe the behavior of the measurement process.

day

CO2 Level

1	12.9	12.1	13.8
2	13.2	13.2	12.7
3	13.3	13.5	13.5
4	13.1	12.2	12.3
5	13.2	13.2	12.5
6	13	13	12.9
7	12.5	13.8	13.2
8	12.7	13.4	13
9	12.8	12.7	13.6
10	12.7	12.9	13.4
11	12.9	12	13.3
12	12	13.7	13.1
13	12.9	13.1	13
14	12.8	13.6	13.3
15	12.7	13.6	13.2

Answer 1

It is a problem of statistical quality control.

Here we are to use the Xbar-Rchart as the sub-sample size given in the problem i.e the no. of sample for each day on the co2 emission of the process is 3(<10). All the other theoretical details are given in the solution below. A control chart help us to find whether the process mean and variance is in control or not.