Below is an argument from a recent Newsweek article about electric toothbrushes. What follows is the beginning of an analysis of this argument following the instructions for the separate arguments for the assignment due on 1/30/03.

Statements of “fact” are underlined. Statements of “opinion/belief” are highlighted in yellow.

Statements have been numbered to facilitate construction of the diagram.

From Newsweek, January 27, 2003, Vol. 141, Issue 4

“Less Power to You”

(1) Recent data from 29 clinical trials show that most battery-powered toothbrushes are no more effective at removing plaque than plain old plastic ones. (2) A manual brush is just as good, says dentist Matt Messina, as long as you're not simply "waving your brush at your teeth." (3) Only pricey rotation-oscillation models (those with bristles that circle in one direction, then the other, like the $25-to-$80 Braun Oral-B) perform better, removing 11 percent more plaque. (4) But even that isn't reason to run out and buy one: (5) it may not translate into less chance of gum disease in the long term. (6)"The whole multimillion-dollar market is founded on the weakest of science," says Bill Shaw, who helped compile the data for the Cochrane Oral Health Group. (7) Most trials have lasted less than three months, and the wildly popular SpinBrush has been through very few studies (it wasn't included in the Cochrane report). Shaw, who uses a power brush himself, notes that at least it feels good, and (8) it "isn't worse than a manual brush." In other words, (9) it may not help your teeth, but it won't hurt them, either. (10) We can't say the same for your wallet.

What is the main conclusion? It is implied in statement (10). “We can’t say the same for your wallet” can be taken to mean “Electric toothbrushes are not worth the cost.”

Which statements support this claim? Consider them individually.

1. Most battery powered toothbrushes are no more effective … than plain old plastic ones.

2. A manual toothbrush is just as good (as a battery powered one).

3. Only expensive rotation toothbrushes perform better than manual brushes (11% more plaque removal).

4. More plaque removal is not reason to buy a battery powered toothbrush.

5. A battery powered toothbrush may not decrease the chance of gum disease.

6. The multi-million dollar market for powered toothbrushes is founded on weakest science.

7. Most studies of the brushes have lasted less than 3 months and the SpinBrush has been through very few studies.

8. Power toothbrushes are not worse than manual brushes.

9. Power toothbrushes may not help your teeth, but they won’t hurt them, either.

10. MAIN CONCLUSION: Electric toothbrushes are not worth the cost.

• 1 is supported by 3. But 3 is not supported by any other statements. That means that 3 is a BP while 1 is an IC.
• 2 is supported at least by 1, so 2 is an IC.
• 4 is supported at least by 5, so you know that 4 must be an IC.
• 5 does not appear to be supported by any other statement, but it supports 9, so it is a BP.
• 6 is supported at least by statement 7, so you know that 6 is an IC. 7 is not supported by any other statement, so it is a BP.
• 8 follows (perhaps) from 1, and if this is the case, 8 is an IC.
• 9 follows at least from 5 and/or 8.
• 9 leads directly to 10.

Now you have to figure out how to put all the inferences together to lead to the main conclusion.

We will do this in class on 1/30.