This article reports the results of a mixed-methods approach to develop and validate an instrument to measure Indonesian pre-service teachers' conceptions of statistics. First, a phenomenographic study involving a sample of 44 participants uncovered six categories of conceptions of statistics. Second, an instrument of conceptions of statistics was developed on the basis of findings from the phenomenographic study. The instrument was initially piloted with 63 participants. Subsequently, an exploratory factor analysis involving 116 participants, followed by a confirmatory factor analysis involving 232 participants, was executed, suggesting a three-factor structure. In addition, three different types of conceptions of statistical data were identified from the integration of qualitative and quantitative studies. Contributions of the study and implications of the findings for further research and statistics education are discussed.