“…This is the change in sample size used in 21 randomly selected papers on DL-ET in recent years [ 16 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. In Figure 1 , the size of each point represents the size of the sample set used in an article, while different colors are assigned to them for easy distinction.…”