A fourth limitation of the study was the low ICC values for teacher defining comprehension (not able to be calculated), teacher associating comprehension (not able to be calculated), and teacher associating vocabulary (0.508). As noted in Table 3, one rater recorded zero variance on teacher defining comprehension and teacher-associating comprehension in the set of video clips coded by both raters, making it impossible to calculate ICC. Regarding teacher-associating vocabulary, one problem with this code was that it was used relatively infrequently, usually 1 min or less (some-times only a few seconds) for a given observation. Any deviation between the coders would be magnified even if the difference was only a few seconds. For this and other codes with low values and little variance, future use might be facilitated by coding more class-room instruction periods in order to increase the mean levels and variance between coders.