The first example is based on a study that examined the effects of providing praise and preferred edible items based on variable-time schedule in order to reduce problem behavior. In addition, effects of variable-time schedule on compliance were also evaluated. The study was based on a reversal design (ABAB) and included three participants. In the current example, data for one of the participants is provided. Sam was an 8-year-old boy diagnosed with Asperger syndrome and attention deficit hyperactivity disorder. Data displaying frequency of problem behavior and percentage of compliance in each phase of the design are presented in Figure 4 and Figure 5, respectively. Conclusions based on VA of the data suggested that the variable-time schedule reduced problem behavior, but did not increase compliance for Sam. stated that "levels of compliance were only slightly higher during treatment with VT food and praise for Sam ..." and that "variable-time delivery of food and praise superimposed on a demand baseline (in which problem behavior continued to produce escape) greatly reduced problem behavior ..." (p. 431).
ITSA was implemented to evaluate the effect of variable-time delivery on problem behavior and compliance. The ARIMA (1, 0, 0) was applied to both behaviors to estimate 4 parameters: level, change in level, slope and change in slope.
For problem behavior, lag-1 autocorrelation was .40. The analysis for slope and change in slope yielded non-significant findings, whereas change in level in the variable-time delivery phase indicated significant decrease in problem behavior (t (18) = -2.39, p < .05) with medium effect size (d = 1.85) based on tertile distribution. The findings based on statistical analysis confirm conclusions drawn from VA, indicating decrease in problem behavior due to variable-time delivery of preferred food and praise.
For compliance, lag-1 autocorrelation was .13. The analysis for slope and change in slope yielded non-significant findings, whereas change in level in the variable-time delivery phase indicated significant increase in compliance (t (18) = 2.43, p < .05) with medium effect size (d = 1.76). The findings based on statistical analysis did not confirm the conclusions drawn from VA, which indicated only slight increases in compliance, while statistical findings show significant increases with large effect sizes. ITSA details are presented in Table 1.
The second example is based on a study that examined the effectiveness of a device that prevents drivers from changing gears for up to 8 seconds unless the seatbelt is buckled. The study was based on an ABA reversal design and included 101 commercial drivers. Data for one driver is displayed in Figure 6. Based on the VA of the data presented in the top panel, concluded "... an increase in seat belt use following the 8-s delay and a decline when the delay was removed" (p. 377).
ITSA was implemented to evaluate the effect of the 8-s gearshift delay on seatbelt use. Two ARIMA (5, 0, 0) models were applied to test increases in seatbelt use following the 8-s delay (AB) and to test a decline in seatbelt use when the delay was removed (BA). Each model estimated 4 parameters: level, change in level, slope and change in slope. For AB phase of the design, lag-1 autocorrelation was significant (ar1 = .56). The analysis for slope and change in slope yielded non-significant findings, whereas change in level in the 8-s delay phase indicated significant increase in seatbelt use (t (79) = 8.59, p < .05) with large effect size (d = 2.78). The findings based on statistical analysis confirm conclusions drawn from VA, indicating an increase in seatbelt use due to 8-s gearshift delay. For the BA phase of the design, lag-1 autocorrelation was significant (ar1 = .76). The analysis for slope yielded non-significant findings, however change in slope and change in level were significant and indicated a decrease in seatbelt use due to removal of the gearshift delay (t (87) = -2.19, p < .05; t (87) = -8.58, p < .05 for change in slope and change in level respectively). The findings based on statistical analysis confirm conclusions drawn from VA, indicating a decrease in seatbelt use following removal of the 8-s gearshift delay.