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A known disposable razor company is claiming on their web site that their current product is superior to their old one because it has 5 blades instead of three.

You can see the claim on the "science" page here, watching the "Why Fusion is better than MACH3" videoclip.

Do five blades provide any proven advantage in comparison to three blades? For example, less cutting, or a deeper shave? The company only claims it's better, however I don't trust them, as they show only pseudo-scientific crap instead of real facts on their site.

Does any science back their claims?

See also The Economist:

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    While the question is great (+1), I must say that "known disposable razor company" wording is extremely amusing, seeing how you use their brand name 1 line below making the identification 100% unambiguous :)
    – user5341
    Dec 14 '11 at 15:38
  • @DVK I didn't have any choice :-)
    – Sklivvz
    Dec 14 '11 at 16:23
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Studies that have ever been published or scrutinised outside razor companies seem to be rather difficult to come by.

The best I could find was Measurement of beard hair removal efficacy using image analysis, a study conducted by researchers at Gillette (kudos to Solveig_A on Reddit for fetching the full-text for me). Now, a warning: this study's primary focus was not actually about comparing two razors, but on techniques for finding statistically significant results even for marginal effects were to conduct such a study. That can make reading it a bit obtuse (I shall not get into why they might be motivated to conduct such a study...).

The first two experiments compare different types of shaving foam using a twin blade and a single-blade razor, respectively. They do not include results in such a way as to make direct comparison possible. However, the third experiment compared a single-blade and a twin-blade razor (Gillette's Trac I and Trac II razors, respectively) with the same type of shaving foam. According to their data, the twin-bladed razor was 1.6% more effective than the single-bladed razor, but that they could not reject the null hypothesis (that they were equally effective) at the α=0.05 significance level.

In short, this does not represent compelling evidence that a razor with two blades is more effective than a razor with one blade, which does not bode well for the claim that five blades are more effective than three.

Cecil Adams, writing for The Straight Dope, cites studies by Consumers' Research magazine which consistently failed to find a benefit for twin blades, whilst noting that the single-bladed razors tended to last for more shaves than twin-bladed razors.

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