The stimulant Ritalin has been shown to increase attention span and improve academic performance in children with ADHD. To demonstrate the effectiveness of the drug, a researcher selects a sample of n = 25 children diagnosed with the disorder and measures each child's attention span before and after taking the drug. The data show an average attention span of MD = 6.8 minutes with a standard deviation of sD = 5.5 minutes.
Is this result sufficient to conclude that Ritalin significantly improves attention span? Use a one-tailed test with a = .01.