TAKING A CLOSER LOOK: TIME SAMPLING AND MEASUREMENT ERROR¹

Abstract

A person manufactured his in-seat behavior for 15, 30-min sessions so that there were three blocks of five sessions where the behavior occurred 20%, 50%, and 80% of the time. Whole interval, partial interval, and momentary time-sample measures of the behavior were taken and compared to the continuous measure of the behavior i.e., per cent of time the behavior occurred. For interval time sampling, the difference between the continuous and sample measures i.e., measurement error, was: (1) extensive, (2) unidirectional, (3) a function of the time per response, and (4) inconsistent across changes in the continuous measure. A procedural analysis demonstrated that the frequency and duration of behavior are confounded in interval time sampling. Momentary time sampling was found to be superior to interval time sampling in estimating the duration a behavior occurs.

Assessing Observer Accuracy in Continuous Recording of Rate and Duration: Three Algorithms Compared

“…The limitations of the three algorithms suggest that other methods, not in common use, should be investigated as well. Further research with real behavioral streams, theoretical analysis (e.g., Hopkins & Hermann, 1977), scripted behavioral interactions (e.g., Van Acker et al, 1991), and studies with manufactured behaviors (e.g., Powell, Martindale, Kulp, Martindale, & Bauman, 1977) are likely to further influence behavior analysts' choice of appropriate agreement and accuracy algorithms.…”

Use of Discontinuous Methods of Data Collection in Behavioral Intervention: Guidelines for Practitioners

“…Simply put, the briefer the interval duration, the less systematic error will be introduced into a measurement system, regardless of whether PIR, WIR, or MTS are implemented (Devine, Rapp, Testa, Henrickson & Schnerch, 2011;Hanley, Cammilleri, Tiger, & Ingvarsson, 2007;Powell et al, 1975;Powell et al, 1977;Rapp et al, 2008). However, the decrease in interval duration requires additional effort from data collectors and therefore increases the amount of human error that is introduced during measurement.…”

“…MTS is not associated with a characteristic direction of error. Because of this fact, MTS will most commonly provide a more accurate estimate of behavioral duration than either PIR or WIR, although the accuracy will be impacted by variables such as behavior duration or level (Ciotti Gardenier, MacDonald, & Green, 2004;Powell, Martindale, & Kulp, 1975;Powell, Martindale, Kulp, Martindale, & Bauman, 1977).…”

A Method for Describing Preschoolers' Activity Preferences

“…Researchers have evaluated the extent to which the size of the discontinuous sampling interval influences the degree of error (Mudford, Beale, & Singh, 1990;Powell, Martindale, Kulp, Martindale, & Bauman, 1977;Sanson-Fisher, Poole, & Dunn, 1980). These studies have shown that the accuracy of a discontinuous measure is negatively correlated with the length of the interval between measures, and that this relation is also affected by the overall frequency and stability of the target behaviors as well as bout durations (Powell et al, 1977;Saudargas & Zanolli, 1990). Therefore, analysis of the extent of error introduced by intervals of varying lengths is necessary when developing discontinuous methods to measure activities such as the location and engagement of children in a classroom.…”