FURTHER REAPPRAISAL OF MOMENTARY TIME SAMPLING AND PARTIAL‐INTERVAL RECORDING
Alex Harrop, Michael Daniels · Journal of Applied Behavior Analysis · 1993
We found the comments of Suen, Ary, and Covalt (1991) on our paper (Harrop & Daniels, 1986) to be very interesting, and we appreciated the general darity of presentation.On some im- portant points, however, we disagree with their analysis.The comment that "for any given true total duration, MTS can be expected to record behavior in the same number of intervals whether that behavior is massed in one bout or is distributed among many bouts" (p.804) is potentially mis- leading.Consider, for example, a behavior, perhaps a student banging a desk lid in school, that occurs for a total duration of 6 min in a 60-min lesson and that is observed using momentary time samples (MTS) undertaken every 30 s.If the 6 min of behavior occur in one bout, the MTS record would show 12 (perhaps 13) instances recorded, or 12/ 120 of the observations made, which is the correct proportion.If, on the other hand, the behavior occurred in bouts of 3 s each, then the MTS record could conceivably show any number of instances of behavior occurring from 0 to 120 (i.e., from 0/120 to 120/120).That on average, the number recorded in these circumstances would be 12/120 (as may be demonstrated by sampling theory) is, in practice, oflittle use or interest to the practitioner who relies on single periods of observation.Herein