Diagnosis. A study by Joseph Boscarino (Psychosomatic Medicine, Vol.70, pp. 668–676, 2008,) examined the prevalence of heart disease, post-traumatic stress disorder (PTSD), and other problems in more than 4000 Vietnam veterans. The likelihood of death due to heart disease was found to be greater when the PTSD diagnosis was more severe.

a. Do you think that the study is descriptive or inferential? Explain your answer.

b. Is this study observational or experimental? Explain your answer.