MPH

This study investigated the cognitive effects of stimulant medication in children with mental retardation and Attention-Deficit/Hyperactivity Disorder. This case study shows the data for the Delay of Gratification (DOG) task. Children were given various dosages of a drug, methylphenidate (MPH) and then completed this task as part of a larger battery of tests. The order of doses was counterbalanced so that each dose appeared equally often in each position. For example, six children received the lowest dose first, six received it second, etc. The children were on each dose one week before testing. This task, adapted from the preschool delay task of the Gordon Diagnostic System, measures the ability to suppress or delay impulsive behavioral responses. Children were told that a star would appear on the computer screen if they waited "long enough" to press a response key. If a child responded sooner in less than four seconds after their previous response, they did not earn a star, and the 4-second counter restarted. The DOG differentiates children with and without ADHD of normal intelligence, and is sensitive to MPH treatment in these children. Does the drug dose impact performance (measured by the number of correct responses to the DOG task)? We will begin the analysis by looking at baseline (d0) vs. 15 mg (d15). The dataset has been attached to this question. The researchers do not want to assume that the data is normally distributed and wish to proceed with non-parametric testing.