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# Salon versus Drug Store Products: the Tress Test Results

Posted Dec 19 2012 1:01am
 Our loyal readers (both of you) might remember this blog post from a few months ago about comparing salon versus drug store products.  Here’s the quick recap: Heide (a stylist) said drug store hair products leave her client’s hair “silicone impacted.” She says the silicone buildup from drug store products can easily be seen by rubbing her finger nail over the hair. We offered to send her tresses to see if she could really tell the difference. Here’s what’s happened since then…. Heide (who is an AWESOME sport, by the way) agreed to the test so here’s what we did: Treated bleached hair tresses (the same kind of real hair used in testing labs) with two brands of Heide’s choosing: one from the drug store and the other from the salon. The drug store products were Pantene Color Preserve Shine shampoo and conditioner, the salon products were Redken Color Extend shampoo and conditioner. 10 tresses of each were shampooed and conditioned 20 times to simulate about a month’s worth of treatment. We put secret codes on the tresses so Heide wouldn’t know which was which (we even spritzed a little perfume on the hair to mask the scent.) Then, we sent the tresses to Heide so she could perform her “fingernail scrape test.” Would you like to hear the results? First, a word about hair tress testing. In a test set of this size, there’s always the chance that Heide (or anyone else doing such a test) could just guess the right answer. For each individual tress there are two possible answers (either Pantene or Redken) and statistics would say that just purely by chance, a person should be able to correctly identify 50% of the tresses just by guessing. According to my favorite binomial probability calculator, in order to prove that there is more silicone buildup on the Pantene tresses, Heide would have to correctly identify the right product on 15 out of 20 tresses. Anything less than 15 out of 20 means there is no statistical difference between the salon and drug store products (at least using her test method.) Heide correctly identified 8 out of 20 tresses (40%.) In other words, she couldn’t really detect a difference in silicone buildup between these salon and drug store products.  (To be totally fair to Heide, she thought that the tresses felt different than the hair that she is used to. She said that “There is a difference between these kinds of strands and everyday user hair. None of these hairs feel like Redken or Pantene users.”) This was a quick and dirty test but I’m confident that if we repeated it with more tresses the result would be the same.  While we’re pleased that results came out as we predicted (there is no real difference in silicone buildup between drug store and salon products) the important thing is that instead of relying on anecdotal evidence with Heide’s help we were able to actually test a hypothesis. That’s how the scientific method works! Thanks SO MUCH to Heide for agreeing to go along with our experiment. It took a lot of guts to put her beliefs on the line like this and we really appreciate her open mindedness as well as the time and effort she put into this project.