Fig. 4From: Two-stage sampling in the estimation of growth parameters and percentile norms: sample weights versus auxiliary variable estimationModel residuals (left) and Expressive Vocabulary Z-scores (right) as calculated by parameters of the negative binomial auxiliary model (NBAM), weighted, and LMS models based on 1,289 observations. The theoretical shape of the Standard Normal distribution is also superimposed (Standard Normal probability density function (pdf))Back to article page