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Robert Garrard

Publications and source records attributed to Robert Garrard.

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Machine Learning Classifiers Do Not Improve the Prediction of Academic Risk: Evidence from Australia

Machine learning methods tend to outperform traditional statistical models at prediction. In the prediction of academic achievement, ML models have not shown substantial improvement over logistic regression. So far, these results have almost entirely focused on college achievement, due to the availability of administrative datasets, and have contained relatively small sample sizes by ML standards. In this article we apply popular machine learning models to a large dataset ($n=1.2$ million) containing primary and middle school performance on a standardized test given annually to Australian students. We show that machine learning models do not outperform logistic regression for detecting students who will perform in the `below standard' band of achievement upon sitting their next test, even in a large-$n$ setting.

stat.ML

A Goodness-of-Fit Test for Sampled Subgraphs

We consider the problem of testing whether a graph's degree distribution belongs to a particular family, such as poisson or scale-free, given that we only observe a sampled subgraph. In particular, we focus on induced subgraph sampling, a sampling design which systematically distorts the degree distribution of interest. We estimate the parameter indexing the hypothesized family by generalized method of moments and utilize the Kolmogorov-Smirnov test statistic to assess goodness-of-fit. Since the distribution in the null hypothesis has been estimated, critical values for the test statistic must be simulated. We propose a novel bootstrap in which we construct a graph whose degree distribution conforms to the null hypothesis from which we may draw pseudo-samples in the form of induced subgraphs. We investigate the properties of this procedure with a monte carlo study which confirms that the bootstrap is able to attain size close to the nominal level while exhibiting power under the alternative hypothesis. We present an application of this test to the protein interaction network (PIN) of the yeast Saccharomyces cerevisiae. Accounting for the high rates of false negatives present in PIN measurement, we are able to reject the hypothesis that the PIN of S. cerevisiae follows an Erdos-Renyi random graph family of degree distributions.

stat.ME