The document discusses various types of data quality issues that may be present in datasets, including invalid values, different data formats, attribute dependencies, lack of uniqueness, missing values, misspellings, and misfield values. It also presents several techniques that can be used to detect and fix these issues, such as data visualization, outlier analysis, validation code, indicator variables, data binning/bucketing, centering and scaling, and other techniques like grouping outliers or replacing values with frequencies. The overall goal is to clean raw data and ensure it is valid and consistent before use in analysis.