Visualization of Predictive Modeling for Big Data Using Various Approaches When There Are Rare Events at Differing Levels

Visualization of Predictive Modeling for Big Data Using Various Approaches When There Are Rare Events at Differing Levels

Alan Olinsky (Bryant University, USA), John Thomas Quinn (Bryant University, USA) and Phyllis A. Schumacher (Bryant University, USA)
DOI: 10.4018/978-1-5225-3142-5.ch021
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Many techniques exist for predictive modeling of a bivariate target variable in large data sets. When the target variable represents a rare event with an occurrence in the data set of approximately 10% or less, traditional modeling techniques may fail to identify the rare events. In this chapter, different methods, including oversampling of rare events, undersampling of common events and the Synthetic Minority Over-Sampling Technique are used to improve the prediction outcomes of rare events. The predictive models of decision trees, logistic regression and rule induction are applied with SAS Enterprise Miner (EM) to the revised data. Using a data set of home mortgage applications, misclassification percentages of a target variable with a rare event occurrence rate of 0.8% are obtained by running a multiple comparison node. The percentage is varied from 0.8% up to 50% and the results are compared to see which predictive method worked the best.
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Traditional predictive modeling techniques such as logistic regression and decision trees generally work quite well with a nominal target variable. In addition, the newly developed predictive modeling technique of rule induction available in SAS Enterprise Miner (EM) is an alternative method for predicting a bivariate target variable. This technique has shown promise with a rare event target variable which is a bivariate variable in which the event of interest either occurs (1) or does not occur (0) and the rate of occurrence is approximately 10% or less.

However, with a rare event variable, when the data set is very large and the event of interest is very small, all three of these methods typically fail to detect the rare event. This can be particularly true when the percentage of the rare event is extremely small, as in the example presented here, where the rare event occurs in less than 1% of the observations. In this situation, all observations are predicted as being in the group consisting of the more dominant or common event. For example, in the case of a binary target variable, if the rare event makes up only about 1% of the sample, these methods can be correct 99% of the time by predicting all items as falling in the event with the greater probability. In this way, these methods are correct 99% of the time, but may fail to predict the rare event which is most often the aim of the analysis. Unfortunately, many times these rare events, such as fraud, terrorism, etc., are important to predict.

This problem of imbalanced data has been considered before in applications to a variety of fields such as churn models (Guzman 2015, Lemmens & Croux, 2006, Burez & Van den Poel, 2009), credit scoring (Brown & Mues, 2012), crop insurance fraud (Jin & Little, 2005), cyber threats of network intrusions (Dokas et al., 2002), protein classification (Zhao, Li, Chen & Aihara, 2008), telecommunication equipment failures (Weiss & Hirsh, 2000), landslide prediction (Van Den Eeckhaut, et al., 2006), bankruptcy (Foster & Stine, 2004), cardiac surgery (Yap et al., 2014) and detecting rooftops from overhead imagery (Maloof, 2003). King and Zeng (2001) consider modifications to logistic regression to improve model performance. Chawla, Bowyer, Hall and Kegelmeyer (2002) utilize nine different data sets ranging from diabetes to forest cover. In addition, there have been reviews of imbalanced data including Chawla (2005), Visa and Ralescu (2005), Kotsiantis, Kanellopoulos and Pintelas (2006), Han, Yuan and Liu (2009), Sun, Wong and Kamel (2009), Galar, Fernandez, Barrenechea, Bustince and Herrera (2012) and Elrahman and Abraham (2013).

As mentioned, running such an imbalanced model using a data mining software package would fail to detect these important rare events. To try to correct this problem, there are possible methods that have been suggested. These include, among others, oversampling the rare event undersampling the more prevalent event and Synthetic Minority Over-Sampling Technique (SMOTE).

Key Terms in this Chapter

Bivariate Target Variable: The dependent variable in a model for which the outcome of interest is assigned a value of 1 and is assigned a value of 0 otherwise. For rare events, the value is 1 when the outcome corresponding to the rare event occurs.

Logistic Regression: A regression model that is used when the dependent variable is qualitative and a probability is assigned to an observation for the likelihood that the target variable has a value of 1.

False Negative: Model prediction that the target variable has a value of 0 when it really has a value of 1.

Validation Set: A partition of the data set used after the model has been run with the training set, used to help assess the accuracy of the model.

Decision Trees: A predictive model comprised of multiple steps at which each step, the target variable with a value of 1 is assigned to one branch while the target variable with a value of 0 is assigned to the other branch based on the value of another variable in the data set.

False Positive: Model prediction that the target variable has a value of 1 when it really has a value of 0.

Observation: A given realization of the set of variables in a data set. When the columns in a data set correspond to the individual variables, an observation corresponds to one of the rows.

Misclassification: When the model prediction results in a false positive or a false negative.

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