Validity and Reliability of Mathematical Visual Literacy Skills Based on Avgerinou’s Vilual Literacy Index

Abstract

There is much literature on visual literacy across different fields of knowledge. Even so, generally there is a gap of literature that deals with measuring mathematical visual literacy skills. The objective of this paper is to produce empirical data on reliability and validity of mathematical visual literacy skills instrument. The development of items was based on the skills outlined Avgerinou’s VL Index (2007. The early stage in validating the instrument required researchers to seek face validity and content validity from panels of experts. Face validity was based on subjective judgements of the items. Meanwhile, content validity was determined by Content Validity Index (CVI) which is computed using Item-CVI (I-CVI) and Scale-CVI (S-CVI). Each mathematical visual literacy skills had accepted S-CVI values ranging from 0.86 to 1.00 but items with low I-CVI values were deleted. Next, construct validity and reliability was determined by using Exploratory Factor Analysis (EFA) and Cronbach’s alpha respectively. The instrument, consisting of 43 items was assessed on 428 pre-university students. Students’ responses were scored using analytical rubric developed by researchers. Using Principal Component Axis (PCA) and varimax rotation, EFA was carried out where 40 retaining items were extracted to 7 factors, representing each visual literacy skills. Kaiser-Meyer-Olkin (KMO) of 0.721, significant Bartlett’s Test of Sphericity (BTS), communalities anti images ranging between 0.308-0.721 and 0.503-0.835 respectively, 7 extracted factors explaining 53.685% of the total variance, factor loadings of ±0.520 and more, and overall Cronbach’s alphas of instrument recorded at 0.82, explained the complete validity and reliability of the instrument.