ТАBLE P7.48 Sample No. Compressive Strength, MPа Sample Compressive Strength, No. MPa 1 33.9 14 39.8 32.6 15 29.4 3 39.1 16 35.1 4 29.7 17 32.2 42.1 18 35.7 29.8 19 37.5 7 36.1 20 25.5 8 34.1 21 31.1 9 36.1 22 25.4 10 28.9 23 28.3 11 39.8 24 25.4 12 31.2 25 27.0 13 28.0 21 6,

In a ready-mix plant, cylindrical samples are prepared and tested periodically to detect any mix problem and to ensure that the compressive strength is higher than the lower specification limit. The minimum target value was set at 27.6 MPa. The compressive strength data shown in Table P7.48 were collected. Use one system of units only as specified by the instructor.

a. Calculate the mean, standard deviation, and the coefficient of variation of the data.
b. Using a spreadsheet program, create a control chart for these data showing the target value and the lower specification limit. Is the plant production meeting the specification requirement? If not, comment on possible reasons. Comment on the data scatter.