An advertisement for stain remover claimed: STAIN-GONE never fails to remove a stain. Four stained items of clothing were washed, and two questions were asked in each case:
| item | was STAIN-GONE used in the wash? | was the stain removed? |
| 1 | yes | (a) |
| 2 | (b) | yes |
| 3 | no | (c) |
| 4 | (d) | no |