A stepwise method (forward) was used to select traits to predict volume. Forward stepwise multiple regression is a commonly used method for selecting predictor variables in regression analyses. It involves iteratively adding one predictor variable at a time to the model, based on its ability to explain the variation in the outcome variable. Seven variables were used for the model according to the Bayesian information criterion (BIC, Figure 1).

Figure 1. Number of variables analyzed by the forward stepwise method

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