What is a drawback to performing data cleansing (imputation, transformations, etc.) on raw data prior to partitioning the data for honest assessment as opposed to performing the data cleansing after partitioning the data?
A . It violates assumptions of the model.
B . It requires extra computational effort and time.
C . It omits the training (and test) data sets from the benefits of the cleansing methods.
D . There is no ability to compare the effectiveness of different cleansing methods.
Answer: D