Teaching experiments could be performed by a college or university department to find a good introductory textbook, with each text considered a treatment.
tˈiːtʃɪŋ ɛkspˈɛɹɪmənts kʊd biː pɚfˈɔːɹmd baɪ ɐ kˈɑːlɪdʒ ɔːɹ jˌuːnɪvˈɜːsᵻɾi dᵻpˈɑːɹtmənt tə fˈaɪnd ɐ ɡˈʊd ˌɪntɹədˈʌktɚɹi tˈɛkstbʊk, wɪð ˈiːtʃ tˈɛkst kənsˈɪdɚd ɐ tɹˈiːtmənt.