Consider the experiment to study factors that aect the percent removal of arsenic from drinking water using a iron coated sand lter.

(a) Modify the R code in Section 6.5.1 to produce the design shown in Table 6.8.

(b) Determine the dening relation for the experiments in the rst block and show the confounding of main eects with strings of two-factor in-
teractions.

(c) Calculate the eects and make a half-normal plot of them using only the data from block 1 in Table 6.8.

(d) Determine the dening relation for the combined experiments.

(e) Calculate the eects, including the block eect, and make a half-normal plot of them using all the data in Table 6.8. What interactions are con-
founded with the block eect?