PAC analysis, or Personal Attitude Construct analysis, is a case study method developed by Ito (1993, 1994) to measure individual attitude structures. The method involves five steps: (1) free association on a specific theme, (2) similarity ratings among associated items by participants, (3) cluster analysis using similarity distance matrices, (4) participants' reports on their cluster structures and interpretations, and (5) comprehensive interpretation by the experimenter. This session aims to integrate qualitative and quantitative methods to provide an overview of the theory and practical techniques of PAC analysis. The Bayley Developmental Scales is a comprehensive developmental assessment tool consisting of individual cognitive, language, and motor tests, as well as a parent-completed social-emotional and adaptive behavior questionnaire. While it is widely used in English-speaking countries and is considered a global standard in pediatric healthcare, it is not well-known in Japan. The workshop will introduce the content and scoring of the Bayley Scales to those interested in developmental assessment of infants and young children.PAC analysis, or Personal Attitude Construct analysis, is a case study method developed by Ito (1993, 1994) to measure individual attitude structures. The method involves five steps: (1) free association on a specific theme, (2) similarity ratings among associated items by participants, (3) cluster analysis using similarity distance matrices, (4) participants' reports on their cluster structures and interpretations, and (5) comprehensive interpretation by the experimenter. This session aims to integrate qualitative and quantitative methods to provide an overview of the theory and practical techniques of PAC analysis. The Bayley Developmental Scales is a comprehensive developmental assessment tool consisting of individual cognitive, language, and motor tests, as well as a parent-completed social-emotional and adaptive behavior questionnaire. While it is widely used in English-speaking countries and is considered a global standard in pediatric healthcare, it is not well-known in Japan. The workshop will introduce the content and scoring of the Bayley Scales to those interested in developmental assessment of infants and young children.