Concrete blocks to be used in a certain application are supposed to have a mean compressive strength of 1500 MPa. Samples of size 1 are used for quality control. The compressive strengths of the last 40 samples are given in the following table.

Previous results suggest that a value of σ = 15 is reasonable for this process.
a. Using the value 1500 for the target mean μ, and the values k = 0.5 and h = 4, construct a CUSUM chart.
b. Is the process mean in control? If not, when is it first detected to be out of control?

g-/ 4 5 3 7 8 6 9 2 2 3 5 75745718 n- o 7 I 3 8 I 2 6 7 I 8 0 0 0 1 0 1 6 9 8 e-54554554454555555444 123 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 90 73923005397695832294 86907229099184902098 44454554544545455544 p-,1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0