Question: The stimulant Ritalin has been shown to increase attention span and improve academic performance in children with ADHD (Evans, Pelham, Smith, et al.,2001). To demonstrate the effectiveness of the drug, a researcher selects a sample of n=25 children diagnosed with the disorder and measure each child’s attention span before and after taking the drug. The data show an average increased of attention span of Md=6.8 minutes with a standard deviation of s =5.5.