You must have completed the introductory course in statistics, or be in the process of completing it (i.e., currently enrolled in one) by the time you submit your application for admission.
The course may be completed at an accredited college or university that results in credit on an official college transcript. Online courses that earn credit on an accredited college or university transcript meet this requirement. Receiving a score of 5 on an AP Statistics exam also satisfies the requirement, as long as it is documented on a transcript submitted with your application.