title: How to impute the missing value on the test set?
body: <p>I am now handling the missing data. I have missing data in my test and train set. I got a little confused about how to deal with the missing data in the <strong>test</strong> set. If I am imputing by using the "mean" method, should I use the mean calculated from the train set or the test set if I want to impute the missing value in the <strong>test</strong> set. 
  Thank you for helping me!</p>