Rick the receptionist claims that he types an average of 70 words per minute. In order to test this, Rick's boss gives him 15 different one minute typing challenges throughout the day. On each challenge, Rick's boss records the number of words typed. The boss calculates the sample mean to be 67 words per minute and the sample standard deviation to be 16 words per minute. He calculates a test statistic for the following hypothesis test: H0: μ = 70 Ha: μ ≠ 70 Assuming the null hypothesis is true, this test statistic will follow: