Data, Data Types and Descriptive Statistics
            
        
            
    
    
                
            Sahay, A. (2018). Data, data types and descriptive statistics. Business analytics, Volume I : A data-driven decision making approach for business. Business Expert Press.
(Vol. 1, pp. 59 - 78) Chapter 3 describes the classification of data and discusses why such classification is needed, and how it helps in analyzing data.