Robert Burgess 
Key Variables in Social Investigation [PDF ebook] 

Key Variables in Social Investigation encourages sociologists and other social scientists to think about the conceptual and empirical problems of using and evaluating key variables in social research. The book contains reviews of ten major variables: age; gender; race and ethnicity; health and illness; education; social class and occupation; work, employment and unemployment and unemployment; leisure; politics; and voluntary ways in which concepts can be specified and translated into variables and indicators.