Instruments
A total of 32 open-ended algebraic expressions items were constructed for the preliminary study. All these items were adopted and adapted from various educational studies (Kuchemann, 1 Swafford & Brown, 1989; Demby, 1997; Liebenberg, 1997; Vaiyavutja 2001; Teng 2002: 22 & Harries, 2003). These items were divided into 3 levels. These include one-variable and two-variables algebraic expressions items and 10 items with variables in the forms of ab and a2. The preliminary study had encouraged the researcher to examine the types of alternative conceptions that appeared in students' answer scripts. One item from each level with the lowest number of correct responses was analyzed in detail Table 1 shows an example of how the items for two variables were constructed from the preliminary study.