Vacuum cleaner salesperson: To prove that this Super XL vacuum cleaner is better than your old vacuum cleaner, Support I ran your old vacuum once over this dirty carpet. Then Support I ran the Super XL over the same area. Support All that dirt that the Super XL picked up is dirt your old vacuum left behind, proving Conclusion the Super XL is the better vacuum.
The salesperson concludes that the Super XL is the better vacuum because it picked up dirt that the old vacuum missed after both were used on the same area of carpet. The Super XL was used second.
The salesperson's argument is vulnerable to criticism because the vacuums weren't tested under the same conditions. Just because the Super XL picked up some dirt that the old vacuum missed doesn't necessarily suggest that the Super XL is better. In fact, the Super XL might have missed just as much dirt if it had been used first. The salesperson should have tested both vacuums individually to compare how much dirt they each collected on their first pass over equally dirty areas of carpet.
The vacuum cleaner salesperson's argument is most vulnerable to the criticism that it
ignores the possibility that dirt remained in the carpet even after the Super XL had been used in the test
The salesperson never assumes that the Super XL picked up all the dirt in the carpet. Presumably at least a little bit of dirt remained in the carpet after the Super XL was used, but this doesn't change the fact that it picked up dirt that the old vacuum left behind.
takes for granted that the Super XL will still perform better than the old vacuum cleaner when it is the same age as the old vacuum cleaner
The salesperson argues that the Super XL is the better vacuum right now. He never assumes that it will still perform better in 10 years.
takes for granted that because the Super XL outperforms one vacuum cleaner it is the best vacuum cleaner available
The salesperson never claimed that the Super XL is the best vacuum cleaner available, just that it’s better than the old vacuum.
ignores the possibility that the amount of dirt removed in the test by the old vacuum cleaner is greater than the amount of dirt removed by the Super XL
The salesperson’s argument isn’t about which vacuum picked up the greater amount of dirt. He never actually assumes that the Super XL picked up more dirt. Instead, he argues that the Super XL is better because it picked up dirt that the old vacuum left behind.
ignores the possibility that if the Super XL had been used first it would have left behind just as much dirt as did the old vacuum cleaner
The salesperson didn’t test the vacuums under the same conditions. He argues that the Super XL is better because it picked up dirt that the old vacuum missed on its first pass. But it’s possible that the Super XL might’ve left behind just as much dirt if it had been tested first.
Answer five questions and we'll estimate your score.
It takes about five minutes.
Take the free diagnostic