Anonymised dataset

This dataset contains item-level responses to an adapted Japanese version of Oxford’s Strategy Inventory for Language Learning (SILL). As part of a two-stage adaptation and validation study, the same 50-item adapted instrument was administered in both Stage 1 (calibration) and Stage 2 (validation) to undergraduate students enrolled in English-as-a-foreign-language (EFL) courses at two private universities in Japan. Although the final validated scale reported elsewhere comprises 22 items, the present dataset preserves responses to all 50 adapted SILL items collected at both stages, thereby supporting transparency, secondary analyses, and potential revalidation or alternative model testing.