| dc.description.abstract | With the rapid development of information technology, computers can process and store huge amounts of data. This leads to the importance of finding useful content from large amounts of data in data mining. However, many collected datasets for data mining usually contain some missing values, which are likely to degrade the data mining performance.
For incomplete data processing, it is a common and simple way to perform case deletion by ignoring the data samples with missing values if the missing rate was certainly small. Another approach is based on imputation, where various approaches have been proposed for missing value imputation. Generally speaking, the imputation algorithms aim at providing estimations for missing values by a reasoning process from the observed data. However, there is no answer for the question about when should we use the case deletion or imputation approach over different kinds of datasets. Another question is that will performing data pre-processing, i.e. feature and instance selection, affect the final imputation result?
This thesis used 37 different data sets, which contain categorical, numerical, and both types of data, and 5% intervals for different missing rates per dataset (i.e. from 5% to 50%). Research topic is divided into two parts. The experimental results indicate that there are some specific patterns to consider case deletion over different datasets without significant performance degradation. A decision tree model is then constructed to extract useful rules to recommend when to use the case deletion approach. Furthermore, we found that imputation after instance selection can produce better classification performance than imputation alone. However, imputation after feature selection does not have a positive impact on the imputation result. | en_US |