Shoe size data, collected at the beginning of the semester, can be separated according to gender. Let the WCU female population be represented by Us, and the WCU male population be represented by UM. The mean, standard deviation and sample size for both male and female shoe size date is shown in the table below: X S n Female HF 18.4 1.29 17 Male HM 11.3 1.81 16 What is the upper boundary of a 90% confidence interval for the difference of population means HF - HM