Tarbiat Modares University Language Related Research 2322-3081 Articles in Press 2025 07 13 Formal versus Informal Diagnostic Formative Assessment and EFL Learners’ Speaking Fluency and Accuracy Formal versus Informal Diagnostic Formative Assessment and EFL Learners’ Speaking Fluency and Accuracy 7225 10.48311/lrr.2025.7225 FA Mohammad Mahdi Hajmalek Assistant Professor in TEFL, English Language Department, Khatam University Mona Bakhshizadeh Khatam University Journal Article 2025 07 13 Diagnostic Formative Assessment (DFA) has already established its applicability and necessity in second language teaching practice and research as a legitimate supplement to summative assessment. However, examples of practical implementations of DFA informing SLA research and an investigation of the detailed processes involved, especially when it comes to productive skills such as speaking in tertiary educational settings are rather scarce. Therefore, focusing on the formality dimension, as a rather neglected component in DFA, the present quasi-experimental study set out to compare the effects of formal and informal DFA on Iranian EFL learners’ oral fluency and accuracy at university level. For this purpose, a homogeneous group of 52 male and female L2 learners were assigned to two experimental conditions and after a speaking pre-test developed and scored based on IELTS speaking tasks, went through four months of formal and informal DFA based on four reiterative stages of Observation, Initial Assessment, Hypothesis Checking, and Decision Making. Upon the post-test, the results of ANCOVAs showed that both treatments equally contributed to learners’ development of oral fluency and accuracy, indicating that traditional skepticisms towards informal DFA must be revisited and they can serve as appropriate supplements to more formal approaches whenever necessitated by the instruction. EFL practitioners are recommended to take these rather broad, flexible, and convenient informal DFA practices into consideration and decide on their exact choices based on the particularities of the context, situation, and individual learners, which leads to an expansion in their pedagogical options. Diagnostic Formative Assessment (DFA) has already established its applicability and necessity in second language teaching practice and research as a legitimate supplement to summative assessment. However, examples of practical implementations of DFA informing SLA research and an investigation of the detailed processes involved, especially when it comes to productive skills such as speaking in tertiary educational settings are rather scarce. Therefore, focusing on the formality dimension, as a rather neglected component in DFA, the present quasi-experimental study set out to compare the effects of formal and informal DFA on Iranian EFL learners’ oral fluency and accuracy at university level. For this purpose, a homogeneous group of 52 male and female L2 learners were assigned to two experimental conditions and after a speaking pre-test developed and scored based on IELTS speaking tasks, went through four months of formal and informal DFA based on four reiterative stages of Observation, Initial Assessment, Hypothesis Checking, and Decision Making. Upon the post-test, the results of ANCOVAs showed that both treatments equally contributed to learners’ development of oral fluency and accuracy, indicating that traditional skepticisms towards informal DFA must be revisited and they can serve as appropriate supplements to more formal approaches whenever necessitated by the instruction. EFL practitioners are recommended to take these rather broad, flexible, and convenient informal DFA practices into consideration and decide on their exact choices based on the particularities of the context, situation, and individual learners, which leads to an expansion in their pedagogical options.