RESULTS
Overall Study Characteristics
The 55 peer-reviewed studies included in the meta-analysis
were published between 1986 and 2005. A total of 157 participants
were included. Forty-two studies used a variation of
a multiple baseline or probe design, six studies used a reversal
design, three studies used an A–B design, two studies used
a changing conditions design, one study used an alternating
treatment design, and one study used an alternating treatment
and reversal design. Of the 42 studies using a multiple baseline
or probe design, 24 used a multiple baseline–only design,
and 18 used a combination of multiple baseline and changing
conditions, reversal, or alternating treatment design. Interobserver
reliability was reported in all 55 studies. Social validity
was measured in 12 studies, and intervention fidelity was
measured in 14 studies. Experimental control was demonstrated
in 49 studies through the introduction or removal of
the independent variable across three or more points in time.
Interventions ranged in length from 8 to 73 sessions (n = 38,
Mdn = 25.5 sessions). Hours of intervention ranged from 2.5
to 28 hours (n = 18, Mdn = 7.25 hours). Length of intervention
ranged from 10 to 210 days (n = 30, Mdn = 60 days).
Finally, only one study systematically matched the type of intervention
strategy with the type of skill deficit exhibited by
participants.