“…Many researchers in cognitive psychology and mathematics education have identified features that influence item difficulty in many quantitative areas. For example, the determinants of difficulty have been explored for algebra problems (e.g., Embretson, 1995;Heffernan & Koedinger, 1998;Koedinger & MacLaren, 2002;Koedinger & Nathan, 2004;Mayer, Larkin, & Kadane, 1984;Sebrechts, Enright, Bennett, & Martin, 1996), proportional reasoning problems (e.g., Kaput & West, 1994 ;Karplus, Pulos, & Stage, 1983;Noelting, 1980;Vergnaud, 1980), arithmetic word problems (e.g., Kintsch & Greeno, 1985;Riley & Greeno, 1988), and quantitative reasoning items with more than one correct response (Bennett et al, 1999;Katz, Lipps, & Trafton, 2002).…”