Some of the prior intervention programs did not produce
positive effects for critical outcomes measured in the studies
(Cobiella et al., 1990; Harrison. Sherrod. Dunn. Olivet. S
Jeong 1991: Rauh. Achenbauch. fNurcombe, Howell. & Teti,
]998; White-Traut & Nelson. 1988). However, the sample
sizes in these studies were small. As a result, power in these
studies may not have been sufficient to detect statistically
significant differences between the experimental and control
groups.