A researcher wants to determine if MDMA assisted therapy has an effect on post-traumatic stress disorder (PTSD) symptoms in a cohort of US Marine veterans. The researcher gave one dose of MDMA or placebo, along with a therapy session; the veterans were asked to self-report their anxiety levels three days before and after the therapy session. The data is summarized in the table below. ANXIETY LEVELS Decrease No Decrease With MDMA 513 223 Placebo 293 397 Calculate the odds ratio (OR) of veterans who had MDMA assisted therapy and had a decrease of anxiety levels.

a. OR= 0.98

b. OR= 1.698

c. OR= 1.067

d. OR= 3.117

e. OR= 1.763