[Im Just A Bill]

Just calculate based on individual data points of your return. If you want to make independant of entry fee size, just divide. So, for a loss your data would be -30/30 or -1 (1 entry fee loss). For 3rd place, 30/30=1 (or a 1 entry fee win), etc. From the data points, you can easily calculate mean and sd using standard stats forumlas.