“…In most studies, researchers used factor analyses to demonstrate that the different PLC dimensions could be distinguished as separate factors (e.g., Bryk, Camburn, & Louis, 1999;Hipp, 2005;Visscher & Witziers, 2004;Wahlstrom & Louis, 2008), while in other studies, researchers used a standardized index that represented the sum of separate factors to operationalize professional community (e.g., Louis et al, 1996;Louis & Marks, 1998;Marks & Louis, 1999). In only one study did researchers use second-order factor analyses to determine whether the separate dimensions measured a single underlying organizational construct, professional community (Bryk et al, 1999).…”