Preprocessing Approach for Power Transformer Maintenance Data Mining Based on k-Nearest Neighbor Completion and Principal Component Analysis

Table 3

Statistical data before any imputation.

Variable	Obs	Obs. with MV	Obs. without MV	Mean	Standard deviation
H2	31	2	29	80,034	19,320
CH4	31	1	30	30,387	10,246
C2H4	31	1	30	31,080	10,918
CO	31	1	30	1174,400	298,059
CO2	31	1	30	9159,467	3057,737
O2	31	0	31	5591,968	5126,700
N2	31	2	29	71206,679	10819,652