MARCO CONCEPTUAL

To examine potential indirect pathways, Baron & Kenny’s (1986) guidelines for testing mediation models were followed to determine full or partial mediated pathways. According to Baron and Kenny (1986) a variable is confirmed as a mediator variable if the following four conditions are satisfied:

1. The independent variable must be significantly associated with the mediating variable (Path A).

2. The proposed mediating variable must be significantly associated with the dependent variable (Path B).

3. The independent variable must be significantly associated with the dependent variable (Path C).

4. In the fourth condition the beta coefficient for the independent variable must be non-significant in the presence of the mediating variable (mediation) (see Figure 4). If the beta coefficient is reduced but still significant, then it can be concluded that the effect of the independent variable on the dependent variable is only partially mediated.

To perform mediated hierarchical regression Tabachnick & Fidell (2007) recommended using an alpha level of .05 to test conditions 1 to 3 and .01 to assess condition 4. The more conservative level compensates for the experiment wise error rate associated with a multiple number of regression analyses.

Figure 4. Schematic diagram of a mediated relationship. (adapted from Baron & Kenny (1986, p. 1176)

The following hypotheses, related to the mediating role of maternal cognitions about infant sleep-SAD and the mediating role of active physical comforting, were tested.

15. The positive association between trait anxiety and infant sleep outcome will be mediated by maternal cognitions about infant sleep-SAD.

16. The positive association between maternal sleep history and infant sleep outcome will be mediated by maternal cognitions about infant sleep-SAD.

17. The positive association between maternal cognitions about infant sleep-SAD and infant sleep outcome will be mediated by active physical comforting.

The results from the testing of these hypotheses are presented below with the statistical output for hypotheses 15 and 17 included as Appendices O and P.

Results from the testing of hypothesis 15 showed that trait anxiety was

significantly associated with maternal cognitions about infant sleep-SAD thus satisfying condition 1 for establishing maternal cognitions about infant sleep–SAD as a mediator

between trait anxiety and infant sleep outcome (β = .37, p < .001). Maternal cognitions about infant sleep–SAD were found to be significantly associated with the outcome variable infant sleep outcome (β = .43, p < .001). Thus, condition two for inferring mediation was met. Condition three was also satisfied as trait anxiety was significantly associated with infant sleep outcome (β = .28, p < .01).

In order to infer full mediation, the association between the independent variable, trait anxiety, and the dependent variable, infant sleep outcome, needed to be non-significant when the effects of the mediator variable, maternal cognitions about infant sleep–SAD was entered into the model. The direct effect of trait anxiety on infant sleep outcome, after controlling for maternal cognitions about infant sleep–SAD, was not statistically significant (β = .14, p >.05), indicating no relationship between trait anxiety and infant sleep outcome when controlling for maternal cognitions about infant sleep–SAD. This result indicates that maternal cognitions about infant sleep–SAD fully mediated the relationship between trait anxiety and infant sleep outcome. The mediation result was confirmed by a Sobel test (Aroian, 1947) conducted using the calculation tool provided by Preacher and Leonardelli (2006). The z score (2.94, p < .01) indicated the significance of the mediation effect. The effect of the mediator variable, maternal cognitions about infant sleep-SAD, on the association between trait anxiety and infant sleep outcome is depicted in Figure 5 below.

It was hypothesised that maternal cognitions about infant sleep–SAD would mediate the association between maternal sleep history and infant sleep outcome. Maternal sleep history, however, was not significantly associated with maternal cognitions about infant sleep–SAD (β = .16, p > .1). Thus condition 1 for establishing maternal cognitions about infant sleep-SAD as a mediator between maternal sleep history and infant sleep outcome was not satisfied. As condition 1 was not satisfied further testing was not relevant.

Results from the testing of hypothesis 17 indicated that condition one was met with maternal cognitions about infant sleep–SAD being significantly associated with the mediator variable active physical comforting (β = .36, p < .001). Active physical

comforting was significantly associated with the outcome variable infant sleep outcome

(β = .47, p < .001). Thus, condition two for inferring mediation was met. Condition

β

(

β

β

β

Figure 5. Maternal cognitions about infant sleep-SAD as a mediator of the association between trait anxiety and infant sleep outcome.

Note. The number in parentheses is the standardized beta weight for the direct pathway between the independent and outcome variable.

three was also satisfied as maternal cognitions about infant sleep–SAD was significantly associated with infant sleep outcome (β = .42, p < .001).

In order to infer full mediation the beta coefficient for the association between the independent variable maternal cognitions about infant sleep–SAD and the outcome variable infant sleep outcome must be non-significant when the mediator variable active physical comforting is entered into the model. The effect of maternal cognitions about infant sleep–SAD on infant sleep outcome, after controlling for active physical

comforting was reduced but remained statistically significant (β = .30, p < .01), indicating a relationship between maternal cognitions about infant sleep–SAD and infant sleep outcome when controlling for active physical comforting. Results indicate that the association between infant sleep outcome and maternal cognitions about infant sleep–SAD was partially mediated by active physical comforting. The partial mediation result was confirmed by a Sobel test (Aroian, 1947) conducted using the calculation tool provided by Preacher and Leonardelli (2006). The z score (3.56, p < .001) indicated the significance of the partial mediation effect. The effects of the mediator variable active physical comforting on the association between maternal cognitions about infant sleep– SAD and infant sleep outcome is depicted in Figure 6 below.

Figure 6. Active physical comforting as a mediator of the association between maternal cognitions about infant sleep-SAD and infant sleep outcome.

Note. The number in parentheses is the standardized beta weight for the direct relationship between the independent and outcome variable.

* p < .05. ** p < .01 ***. p < .001.

A revised version of the Model showing direct and indirect pathways is shown in Figure 7 below.

β

(

β

β

Figure 7. Revised model of the maternal factors influencing infant sleep outcome. Note. Direct Pathways

Indirect Pathway (Maternal cognitions about infant sleep-SAD as a mediator of the association between trait anxiety and infant sleep outcome). Indirect Pathway (Active physical comforting as a mediator of the association between maternal cognitions about infant sleep-SAD and infant sleep outcome).

* p < .05. *** p < .001.