A coagulation-microfiltration process for removing bacteria from water was investigated in Environmental Science & Engineering (Sept. 1, 2000). Chemical engineers at Seoul National University performed a designed experiment to estimate the effect of both the level of the coagulant and acidity (pH) level on the coagulation efficiency of the process. Six levels of coagulant (5, 10, 20, 50, 100, and 200 milligrams per liter) and six pH levels (4.0, 5.0, 6.0, 7.0, 8.0, and 9.0) were employed. Water specimens collected from the Han River in Seoul. Korea, were placed in jars, and each jar was randomly as- signed to receive one of the 6 × 6 = 36 combinations of coagulant level and pH level.
a. What type of experimental design was applied in this study?
b. Give the factors, factor levels, and treatments for the study.