Bordens, K. S. & Abbott, B. B. : Research Design and Methods A process approach, 2005. McGraw-Hill. ISBN:?0072887648. 8.ed, Kap. 1-14 (OBS. ed. 7, Kap.1-14, ed. 6 Kap. 1-13).
Howitt, D. & Cramer. D: Introduction to Statistics in Psychology, 2008. Pearson Prentice Hall. 4. utgave. Kap: 1-18.