Do Children Diagnosed with Attention Deficit/hyperactivity Disorder (ADHD) Have Smaller

Short Answer

Do children diagnosed with attention deficit/hyperactivity disorder (ADHD) have smaller brains than children without this condition? Brain scans were completed for 152 children with ADHD and 139 children of similar age without ADHD. The mean brain size for the 152 children with ADHD was 1059.4 mL with a standard deviation of 117.5 mL. The mean brain size for the 139 children of with-out ADHD was 1104.5 mL with a standard deviation of 111.3 mL.
-The standard deviation of a simulated null distribution of 1,000 differences in sample mean brain sizes was 13.4 mL. Calculate the standardized statistic for a test of two means (ADHD - Without ADHD).