Calculation of a Health Index of Oil-Paper Transformers Insulation with Binary Logistic Regression

Table 2

Model summary with six factors.

Step	−2 log likelihood	Cox & Snell- Square	Nagelkerke- Square
1	12.333	0.557	0.790

Cox & Snell- Square, similar to Nagelkerke- Square, represents the whole validity of the logistic regression model and measures the proportion of data variation explained by the independent variables in logistic model; more information about it can be got from [23].