This is the answer

The first column is the room, the second is the person's name, the third is the item tested, and the fourth is the number of participants. This arrangement satisfies all the conditions, as shown below.

1. The room with the most participants is not room A.

2. Farley's group has the same number of participants as Brent's adjacent group; Brent's group is not testing salad dressing.

3. The magazine group is in room B, which is before room C, where Brent's 12-person group meets. Brent's group in room C comes before Farley's group in room D.

4. Wilma's group has half as many members as Brent's group. Brent's group is in room C.

5. The video game group is Wilma's group. The 14-member group is the one in room B.

6. Each tester and test item is assigned to a unique room.