Freedman, Pisani, and Purves (2007) ምዕራፎች 1 እና 2 መካከል በተደረጉ ሙከራዎች, ቁጥጥር በሚደረግባቸው ሙከራዎች እና በአጋጣሚ በተደረጉ የቁጥጥር ሙከራዎች መካከል ያለውን ልዩነት ግልፅ የሆነ መግቢያ ያቀርባሉ.
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.