A paper discussing the development of construct validity as applied to psychological studies.
The sixth chapter of an online Introduction to Biostatistics course. Three sets of lecture notes are provided (only the first one works). Additionally, links for additional reading and exercises with solutions are provided.
This chapter of the "Concepts and Applications of Inferential Statistics" online textbook describes in detail the Kruskal-Wallis test, it's formulas, variables, and procedures using an example involving wine-tasters.