Nicholls, Polman, Levy, and Backhouse (2009) measured mental toughness (among other measures) in a sample of athletes ranging in age from 15 to 58 years. They reported that "males scored significantly higher than females on total mental toughness" (Nicholls et al., 2009, p. 74). Is it possible that an experimental method was used to show this effect? Explain.