Statistical Evaluation of Ensemble Learning Outcomes for Missing Value Problem in Imbalanced Class Distribution

Öz

Rapid developments in technology have brought data in different structures and high dimensions in recent decades. Due to this rapid changes and problems encounters in data sets, it has been inevitable that traditional methods replaced with machine learning methods. Within the range of this study, two important data problems are discussed: data sets with i) missing observations and ii) imbalanced class distribution. This study aims to fill the datasets that have both missing observation and imbalanced class distribution problems at the same time by using various missing observation imputation methods and to assess the success levels of ensemble learning algorithms on the obtained data. In the data set collected through sensors for the application, there are 59000 observations for training versus 1000 positive observations for the negative class. The models obtained were tested with the data with an imbalanced class distribution of 2.4%. In addition, approximately 99% of the features in the data set have missing data up to 82%. These missing observations have been tried to be eliminated by hot deck imputation, mean, median, mode, multiple imputation, expectation maximization, and k nearest neighbour methods. Datasets completed with the imputation methods were comparatively tested with algorithms such as Extra Trees, Random Forest, Gradient Boosting, LightGBM, and XGBoost, and the most promising result was obtained with the XGBoost algorithm.

Anahtar Kelimeler

• Missing data imputation
• Class imbalanced learning
• Ensemble Learning
• Statistical Evaluation
• Wilcoxon Rank Test
• XGBoost

Dengesiz Sınıf Dağılımında Kayıp Gözlem Sorunu için Topluluk Öğrenmesi Sonuçlarının İstatistiksel Değerlendirmesi

Öz

Son yıllarda gelişen teknoloji sürekli akan, farklı yapılarda ve yüksek boyutlarda verileri de beraberinde getirmiştir. Bu hızlı değişim ve veri setlerinde rastlanan problemler özellikle geleneksel yöntemleri bir noktadan sonra yetersiz bırakmaktadır. Bu çalışma kapsamında iki önemli veri problemi ele alınmıştır: i) kayıp gözlem içeren veri setleri ve ii) dengesiz sınıf dağılımı içeren veri setleri. Bu çalışmanın amacı aynı anda hem kayıp gözlem hem de dengesiz sınıf dağılımı sorununa sahip veri setlerini çeşitli kayıp gözlem atama yöntemleri kullanarak doldurmak ve elde edilen veri üzerinde topluluk öğrenme algoritmalarının başarı düzeylerini değerlendirmektir. Uygulama için sensörler aracılığıyla toplanan veri setinde eğitim için 59000 gözlemden oluşan negatif sınıfa karşılık 1000 adet pozitif sınıfa ait gözlem bulunmaktadır. Elde edilen modeller %2.4 oranında dengesiz sınıf dağılımına sahip sınama verisi ile sınanmıştır. Ayrıca veri setinde bulunan değişkenlerin yaklaşık %99’unda %82’ye varan kayıp veri söz konusudur. Bu kayıp gözlemler sıcak deste ataması, ortalama, ortanca, tepe değeri, çoklu atama, beklenti en büyükleme ve k en yakın komşu yöntemleri ile giderilmeye çalışılmıştır. Atama metodu ile eksik veri tamamlaması yapılan veri setleri Extra Trees, Random Forest, Gradient Boosting, LightGBM ve XGBoost gibi algoritmalar ile karşılaştırmalı sınanmış, en iyi sonuç XGBoost algoritması ile elde edilmiştir.

Anahtar Kelimeler

• Kayıp veri atama
• Dengesiz sınıf öğrenmesi
• Topluluk Öğrenmesi
• İstatistiksel değerlendirme
• Wilcoxon Sıra Testi
• XGBoost

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