A medical researcher reads an article in Today's Health-Conscious Woman magazine about the benefits of using the phytochemical capsaicin to treat knee pain. She asks 10 people with arthritic knees to rub a cream that contains the phytochemical on their knee joints for 2 weeks. At the end of the 2 weeks, the researcher asks the subjects whether their knee pain improved, stayed about the same, or worsened during the treatment period. After collecting responses from the people, the researcher reports the results of her study during a popular TV show that is hosted by a doctor. Based on this information, which of the following statements is true?
a) Capsaicin is proven to treat knee pain
b) The study lacks a control group
c) Knee pain worsened for all participants
d) The phytochemical had no impact on knee pain