What is the probability that he is telling the truth? 

It is generally assumed that 75% of type-I diabetics comply with their insulin regimen. Suppose that a 12-year-old type-I diabetic boy comes to clinic and shows a 5-lb. weight gain over 1 year (actually, because of measurement error, assume this is an actual weight gain from 4.5 to 5.5 lbs.). The boy claims to be taking his insulin medication.