Research Methods Knowledge Base. Un interesante recurso sobre metodología de investigación

Explica con claridad los principales fundamentos de la investigación cualitativa y cuantitativa. Algunos métodos están explicados con profundidad y otros son sólo una introducción que deberá ampliarse por otras vías. Pero me parece que es completo, es gratis y está accesible on-line ¿se puede pedir más?:
Trochim, W.M.K. (2006). Research Methods Knowledge Base (http://www.socialresearchmethods.net/kb/index.php)

The Research Methods Knowledge Base is a comprehensive web-based textbook that addresses all of the topics in a typical introductory undergraduate or graduate course in social research methods.  It covers the entire research process including: formulating research questions; sampling (probability and nonprobability); measurement (surveys, scaling, qualitative, unobtrusive); research design (experimental and quasi-experimental); data analysis; and, writing the research paper.  It also addresses the major theoretical and philosophical underpinnings of research including: the idea of validity in research; reliability of measures; and ethics.  The Knowledge Base was designed to be different from the many typical commercially-available research methods texts.  It uses an informal, conversational style to engage both the newcomer and the more experienced student of research.  It is a fully hyperlinked text that can be integrated easily into an existing course structure or used as a sourcebook for the experienced researcher who simply wants to browse.