2.3 Why need data pre-processing? Garbage in,garbage out-dirty data; .Data-gathering methods are often loosely controlled; .Irrelevant and redundant information present; .Noisy and unreliable data; Reference:S.Kotsiantis,D.Kanellopoulos,P.Pintelas,"Data Preprocessing for Supervised Leaning",International Journal of Computer Science,2006, Vol1N.2,pp111-117. ATA 25 Copyright 2019 by Xiaoyu Li.Copyright © 2019 by Xiaoyu Li. 25 2.3 Why need data pre-processing? Garbage in, garbage out—dirty data; Data-gathering methods are often loosely controlled; Irrelevant and redundant information present; Noisy and unreliable data; Reference: S. Kotsiantis, D. Kanellopoulos, P. Pintelas, "Data Preprocessing for Supervised Leaning", International Journal of Computer Science, 2006, Vol 1 N. 2, pp 111–117