I have an average purchase amount about $102 in the population(sample size 8,091). The standard deviation is about $189(big). The whole data heavily right skewed. I want to take out the outliers when I do statistical difference testing. I have two questions here.
1. Can I get it directly from the data or I need to do LOG transformation? Since the data looks normal after the log transformation.
2. How can I take off the outliers? From the original data or Log transformed data. Should I use 3xstandard deviation rule or top 5% extreme value rule?
Any help will be highly appreciated.