**Partial leverage** is used to measure the contribution of the individual independent variables to the leverage of each observation. That is, if *h*_{i} is the *i*th row of the diagonal of the hat matrix, the partial leverage is a measure of how *h*_{i} changes as a variable is added to the regression model.

The partial leverage is computed as:

where

*j*= index of independent variable*i*= index of observation*X*_{jยท}= residuals from regressing*X*_{j}against the remaining independent variables

Note that the partial leverage is the leverage of the *i*th point in the partial regression plot for the *j*th variable. Data points with large partial leverage for an independent variable can exert undue influence on the selection of that variable in automatic regression model building procedures.

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