Statistics are important tools used everyday in fields such as medicine, business, sports, research, and advertising. Sometimes, in order to promote sales of a product, advertisers will use misleading statistics. The ad you referenced in your question uses the claim of being "the #1 dermatologist recommended brand". Often, advertisers will use a fraction or percent to advance their claim. This sounds very persuasive to a consumer, right? Dermatologists are professionals that treat thousands of patients a year and certainly they would know what brand works. Hold on though, as a savvy consumer, the claim's validity must be considered. Exactly what type of dermatologist sample was used? (A statistical sample consists of the individuals, objects, or measurements selected by the collector from the population.) Was this sample of dermatologists randomly selected and how large was the actual sample? Perhaps the ad claim was based on just a handful of dermatologists or a group of dermatologists that hold stock in that brand's company, or maybe they just received a big box of free samples. That would make the claim less than impressive and misleading.
Another example: "9/10 students at XYZ School believe the school should require sports participation." That's a strong number but what if the surveyor only questioned the football players as they exited the locker room? The sample would not be representative of the school's student body and therefore would be misleading.