The document discusses descriptive data summarization techniques for data cleaning and preprocessing. It describes common issues with real-world data including missing values, noise, and inconsistencies. Common techniques for data cleaning are then presented, such as data cleaning, integration, transformation, and reduction. Methods for handling missing values, smoothing noisy data, and resolving inconsistencies are outlined. Finally, descriptive statistical techniques for summarizing data distributions are reviewed, including measures of central tendency, dispersion, and graphical displays like histograms and scatter plots.