Variability analysis using CAF measures
May Yue Wu, Rasmus Steinkrauss, Wander M. Lowie · Research methods in applied linguistics · 2025
Abstract This chapter examines potential challenges for longitudinal L2 studies using quantitative CAF (complexity, accuracy, and fluency) measures. For a period of 13 months, we followed the CAF development of two L2 English students, collecting multiple samples at each monthly data point for several CAF measures with different levels of reliability. We then plotted multiple developmental trajectories by randomly selecting one single result from each time point. Comparing the resulting trajectories for high-, medium-, and low-reliability CAF measures, noticeably different developmental paths emerged for low-reliability measures for the same measure and participant. These distinct trajectories confirm that low-reliability measures are inadequate for capturing meaningful variability ( Wu et al., 2023 ; Wu, 2025 ) when measured only once at each data point.