The data shown here represent a single replicate of a 25 design that is used in an experiment to study the compressive strength of concrete. The factors are mix (A), time (B), laboratory (C), temperature (D), and drying time (E).

(a) Estimate the factor effects.

(b) Which effects appear important? Use a normal probability plot.

(c) Determine an appropriate model and analyze the residuals from this experiment. Comment on the adequacy of the model.

(d) If it is desirable to maximize the strength, in which direction would you adjust the process variables?

(1) a b 700 = 900 e be abc 3400 ab = 5500 600 ce C ac 1000 bc = = 3000 abc = 5300 ,, = ace = 800 = 1200 3500 = 6200 = 600 1200 bce = 3000 abce = 5500 d 1000 de 1900 ad = = 1100 ade = 1500 bd = 3000 bde 4000 abd = 6100 abde = 6500 cd 800 cde 1500 acd 1100 acde = 2000 bcd = 3300 abcd = 6000 bcde = 3400 abcde = 6800