An experiment was performed to enhance the yield of chemical process. Four factors were selected, and two replicates of the completely randomized experiment were run. The results are shown in following table:
| Treatment |
Replicate |
Replicate |
Treatment |
Replicate |
Replicate |
| Combination |
I |
II |
Combination |
I |
II |
| (1) |
90 |
93 |
d |
98 |
95 |
| a |
74 |
78 |
ad |
72 |
76 |
| b |
81 |
85 |
bd |
87 |
83 |
| ab |
83 |
80 |
abd |
85 |
86 |
| c |
77 |
78 |
cd |
99 |
90 |
| ac |
81 |
80 |
acd |
79 |
75 |
| bc |
88 |
82 |
bcd |
87 |
84 |
| abc |
73 |
70 |
abcd |
80 |
80 |
a. Determine the factor effects.
b. Find out which factors are important in the explaining yield.