"Tail-Chasing" by Dogs Is an Anxiety Disorder Characterized by Circling

Essay

"Tail-chasing" by dogs is an anxiety disorder characterized by circling behavior withthe dog's attention directed toward its tail. There may be many reasons for tail-chasing behaviors. To investigate the potential for biochemical causes, a study wasperformed at a small animal clinic at a university. Blood samples were taken from arandom sample of 15 dogs brought to the clinic by owners worried about the tail-chasing behaviors of their dogs. A control group consisting of a random sample of 15dogs brought to the clinic for other reasons contributed blood samples with theowner's permission. The mean triglyceride level for the tail-chasing group was 68mg/dl, and the standard deviation was 19.36 mg/dl. The corresponding statistics forthe control group were 61 mg/dl and 11.62 mg/dl. Both sample distributions wereapproximately symmetric.
a) Is there convincing evidence of a difference in mean triglyceride level in thesetwo populations?
Provide statistical justification for your response.
b) Irrespective of your response in part (a), consider the design of this study. Woulda statistically significant difference in mean triglyceride levels be sufficient tomake a case that triglyceride level is a cause of tail-chasing behavior in dogs?
Why or why not?