| Children come to school with a number of informal math skills (Gersten et. al., 2005; National Mathematics Advisory Panel, 2008). These informal skills include counting, ability to identify numbers, ability to formulate mental number lines, and ability to discriminate between quantities (Clements, Sarama, & DiBiase, 2004). Tests of Early Numeracy (TENs), Quantity Discrimination (QD) being one, are robust indicators that are based on numeracy skills and can be used to help educators identify students potentially at-risk for later failure in formal mathematical computation (Clarke & Shinn, 2002). There is no current single TEN that accounts for enough of the variance in informal math that can be used as an independent screening measure for early numeracy. This study investigated changing probe construction for the QD measure from finding the larger of two numbers to finding the middle number of a three item set to improve the concurrent validity with the Number Knowledge Test (NKT), so it possibly could be used as an independent measure for early numeracy. If a broader range of informal math skills could be investigated within one measure, as was suggested in this study by changing probe construction, then it is possible that the validity of that measure could be increased. Changing the probe construction from finding the larger of two numbers to finding the middle number of a three number set did not improve the validity of the original QD measure in this study. Whether administration time and scoring method could impact the validity was questioned as well. Neither changing the administration time from one minute to two or three minutes, nor changing the scoring of the QD measure from a purely fluency based measure to an outcome measure that takes into account fluency while weighting the score for accuracy improved the validity of the original QD measure. Theoretical, research, and applied implications regarding the findings of this study, as well as how the study findings could possibly affect future directions for early numeracy CBM screening and CBM screening in general are discussed. |
