(revised) Manual 2012 (2).pdf - e-asTTle

6.2.2.Writing scores in the sampleFigure 5 shows a box plot of the distribution of writing scale scores for each year-level in the sample. The boxplot displays – in ascending order – the fifth percentile, the lower quartile, the median, the upper quartile andthe ninety-fifth percentile of the writing scores. The medians exhibit a typical curved growth pattern. Thevariation in writing scores (as indicated by the interquartile range) is somewhat larger for year-levels 1, 2 and3 than for the remaining year-levels.Figure 5 e-asTTle writing sample score distributions by year-level6.3.Constructing the e-asTTle reference dataThe e-asTTle application is designed to provide a substantial amount of reference information. For example,it requires summary statistics for the distribution of writing scores (simultaneously) broken down by yearlevel,gender and ethnicity. The scope of the current work meant that some of the year-level-by-gender-byethnicitycells were too small to produce summary statistics that were suitably robust. Similarly, the e-asTTletool requires all normative information for each quarter of the school year. This was also outside the scope ofthe current e-asTTle work.To compile the normative data required by the application a linear regression model of the e-asTTle sampledata model was used to:summarise the information contained in the e-asTTle sample in an efficient, yet accurate way1.provide a robust method for estimating the means and standard deviations needed to produce the2.normative information that is required by the e-asTTle tool.Page 34 Part B: Technical informatione-asTTle writing (revised) Manual