Joan conducted a study to see how common binge drinking is on her college campus. She defined "frequent binge drinking" as having five or more drinks in a row three or more times in the past two weeks. Out of 593 students who replied to her survey, 64 fit this criterion. Joan wants to construct a significance test for her data. She finds that the proportion of binge drinkers nationally is 13.1%. The z statistic for this data is .