Henry is researching the efficacy of a new drug for treating agoraphobia (fear of public places). His assistant, who is unaware of the study’s purpose, randomly assigns half of his 200 subjects a 30 day supply of the drug (Fearnot) and the other half a 30 day supply of a placebo (i. e., sugar pill). A month later the subjects are given a questionnaire to rate their fear of being in public. Henry finds that there is no difference between the two groups in their level of fear. How many subjects participated in this study?