Creating a variable in Alteryx

Hi ,

I have 500000 variables. I need to create a string cloumn with 20 % of 500000 population as 'first time freshman', 60 % of 500000 population as 'first time transfer' and remaining 20 % as 'third year'

can some one please help me in doing that in alteryx. I thank you in advance.

-Bharath