Final answer:
The assertion that a 15% glycolic acid peel contains less glycolic acid than a 50% one is true, since the percentage reflects the concentration of glycolic acid.
Step-by-step explanation:
The statement that a 15% glycolic acid peel has less glycolic acid than a 50% glycolic acid peel is true. This is because the percentage indicates the concentration of glycolic acid in the peel formulation. A product with a higher percentage has a higher concentration of the active ingredient. Thus, 50% is a much higher concentration than 15%, therefore more glycolic acid is in the 50% glycolic acid peel.