Medicine and Clinical Studies
A recent study in Nova Scotia, Canada, suggested that several factors affect the age at diagnosis of autism spectrum disorders (ASD).15 Suppose an additional study was conducted to determine whether age at ASD diagnosis is affected by county and a diagnosis of attention-deficit hyperactivity disorder (ADHD). A random sample of newly diagnosed ASD children was obtained for each combination of county and ADHD diagnosis (1 = no; 2 = yes), and the age of each child was recorded.
a. Construct the ANOVA summary table. Is there any evidence of an effect due to interaction of county and ADHD diagnosis? Use a = 0.05.
b. Is there any evidence of an effect due to county or ADHD diagnosis? Use a = 0.05 for both hypothesis tests. State your conclusions.
c. Early diagnosis of ASD is important in order to begin intervention services. Is diagnosis of ADHD associated with a decrease or increase in age at diagnosis for ASD? Justify your answer.