An experimental design in which neither the investigator nor the subjects are aware of each participant's group assignment is called

The  holy roman empire  was a feudal monarchy that encompassed present-day  germany, the  netherlands,  belgium, luxembourg,  switzerland,  austria, the czech and slovak republics, as well as parts of eastern  france, northern italy,  slovenia, and western  poland  at the start of the early modern centuries. it was created by the coronation of the frankish king  charlemagne  as roman emperor by pope leo iii on christmas day in the year 800, thus restoring in their eyes the western  roman empire  that had been leaderless since 476. charlemagne's frankish successor emperors faltered under political and military challenges, and his inheritance was permanently divided in 887. after 924 the western empire was again without an emperor until the coronation of otto i, duke of saxony, on 2 february 962. this coronation was seen to transfer the roman imperial office to the heirs of the east franks, the germans. the position of emperor remained among the germans until the holy roman empire was abolished in the aftermath of the napoleonic wars in 1806.