The Nature of Science Instrument-Elementary (NOSI-E): the end of the road?

This research continues prior work published in this journal (Peoples, O'Dwyer, Shields and Wang, 2013). The first paper described the scale development, psychometric analyses and part-validation of a theoretically-grounded Rasch-based instrument, the Nature of Science Instrument-Elementary (NOSI-E). The NOSI-E was designed to measure elementary students' understanding of the Nature of Science (NOS). In the first paper, evidence was provided for three of the six validity aspects (content, substantive and generalizability) needed to support the construct validity of the NOSI-E. The research described in this paper examines two additional validity aspects (structural and external). The purpose of this study was to determine which of three competing internal models provides reliable, interpretable, and responsive measures of students' understanding of NOS. One postulate is that the NOS construct is unidimensional;. alternatively, the NOS construct is composed of five independent unidimensional constructs (the consecutive approach). Lastly, the NOS construct is multidimensional and composed of five inter-related but separate dimensions. The vast body of evidence supported the claim that the NOS construct is multidimensional. Measures from the multidimensional model were positively related to student science achievement and students' perceptions of their classroom environment; this provided supporting evidence for the external validity aspect of the NOS construct. As US science education moves toward students learning science through engaging in authentic scientific practices and building learning progressions (NRC, 2012), it will be important to assess whether this new approach to teaching science is effective, and the NOSI-E may be used as a measure of the impact of this reform.

With hiccups and bumps: the development of a Rasch-based instrument to measure elementary students' understanding of the nature of science.

This research describes the development process, psychometric analyses and part validation study of a theoretically-grounded Rasch-based instrument, the Nature of Science Instrument-Elementary (NOSI-E). The NOSI-E was designed to measure elementary students' understanding of the Nature of Science (NOS). Evidence is provided for three of the six validity aspects (content, substantive and generalizability) needed to support the construct validity of the NOSI-E. A future article will examine the structural and external validity aspects. Rasch modeling proved especially productive in scale improvement efforts. The instrument, designed for large-scale assessment use, is conceptualized using five construct domains. Data from 741 elementary students were used to pilot the Rasch scale, with continuous improvements made over three successive administrations. The psychometric properties of the NOSI-E instrument are consistent with the basic assumptions of Rasch measurement, namely that the items are well-fitting and invariant. Items from each of the five domains (Empirical, Theory-Laden, Certainty, Inventive, and Socially and Culturally Embedded) are spread along the scale's continuum and appear to overlap well. Most importantly, the scale seems appropriately calibrated and responsive for elementary school-aged children, the target age group. As a result, the NOSI-E should prove beneficial for science education research. As the United States' science education reform efforts move toward students' learning science through engaging in authentic scientific practices (NRC, 2011), it will be important to assess whether this new approach to teaching science is effective. The NOSI-E can be used as one measure of whether this reform effort has an impact.