ምዕራፍ 1 እና 2 Freedman, Pisani, and Purves (2007) ሙከራዎች, ሙከራዎች መካከል ያለውን ልዩነት ወደ አንድ ግልጽ መግቢያ ይሰጣሉ; እንዲሁም ሙከራዎች በዘፈቀደ.
Chapters 1 and 2 of Freedman, Pisani, and Purves (2007) offer a clear introduction into the differences between experiments, controlled experiments, and randomized controlled experiments.