This document presents a study comparing different scoring functions used in filter-based feature selection methods for microarray gene expression data. Chapter 1 introduces gene expression, DNA microarrays, and the goals of classification and feature selection. Chapter 2 provides background on bioinformatics, molecular biology, and the central dogma. Chapter 3 describes DNA microarray technology and gene expression data. Chapter 4 reviews literature on feature selection techniques applied to microarray data, discussing filter, wrapper, embedded, hybrid, and ensemble methods. Chapter 5 proposes using a scoring function-based filter method to select relevant genes, focusing on mutual information, symmetric uncertainty, information gain, and Chi-square scoring functions.