The primary objective of this work was the scale development of a research-based instrument (EL-Capstone) that may be used to measure EL core-knowledge levels of adults working in an environment with expectations of supporting literacy development of young children. Earlier concept inventory, emergent literacy, and test theory literature informed the framework for this assessment instrument. Designed with three distinct stages, pre-participant, participant, and post-participant, the processes was summarized by six general tasks: (1) define the content, (2) develop and select the instrument items, (3) informal informant sessions, (4) interview sessions with librarians and early literacy practitioners, (5) instrument administration, and (6) evaluation and final refinement. The entire consent-form participant activities centered on developing the items for inclusion in the EL-Capstone inventory. During the first task, the Developing Early Literacy, National Early Literacy Panel (NELP) 2008 Report was adopted as "EL-Expert" surrogates to bind the epistemological framework to the NELP authors' theoretical underpinnings of EL concepts. The NELP Report represents an extremely dense synthesis of the EL experimental and quasi-experimental research. By the end of the pre-participant stage concept-mapping activity, ninety-seven potential instrument items had been constructed that fell into three categories, i.e., predictiveness, definitions, and activities. Accompanying the refined sixty-two items presented during the interview sessions (n=10) were 3 ranking questions, i.e., strength of each concept, difficulty level, and perceived importance. The interview results informed instrument item reductions and modifications. Two alternating online versions of EL-Capstone collected data responses for 30 days from anonymous adult volunteers (n=824). An item response theory two-parameter logistic model (2-PL) was applied during the post-participant stage to identify each item's difficulty and discrimination parameters. When fully developed, this research-based scale may be used to measure EL-levels of adults working in an environment with expectations of supporting literacy development of young children. The subsequent collected information may be used to inform early literacy curriculum development and to support program evaluation.
