Suppose that 10% of interventions tested in the sports science literature are effective at enhancing athletic performance and 90% are ineffective. A small study (n=10 per group) of a new supplement did not find a significant effect for the supplement (p>.05). You estimate that the study had a power of 20% to detect a difference in running times between the two groups. What is the negative predictive value of the study? In other words, what is the chance that the supplement truly doesn't work given that the study found a non-significant result?