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4.3. Structural model assessment

Figure 2. Structural model results
Source: Analysis results from SmartPLS 4.1
The structural model was assessed using multicollinearity diagnostics, explanatory
power (R²), effect size (f²), bootstrapping, and predictive relevance (Q² predict). All inner
VIF values were below 5, indicating no multicollinearity issues.
The model explains 49.4% of the variance in purchase intention (R² = 0.494),
indicating moderate explanatory power. Among the mediators, perceived susceptibility
shows the highest explanatory level (R² = 0.265).
Bootstrapping results support most hypotheses. FOMO significantly influences all
mediators (p < 0.001). In turn, perceived susceptibility, perceived severity, perceived
benefits, and self - efficacy positively affect purchase intention, whereas perceived
barriers show a negative effect and cues to action are not significant.
PLSpredict results indicate that all Q² predict values are above zero, confirming the
model’s predictive relevance.
Overall, FOMO emerges as a key determinant of Gen Z Vietnamese consumers’
online dietary supplement purchase intention in the digital marketplace, particularly
within social media-driven and algorithmically curated environments. In the context of
the rapid expansion of e-commerce platforms and digitally mediated consumption, this
effect operates primarily through cognitive mechanisms related to perceived
susceptibility, perceived benefits, and self-efficacy.
Table 3. Hypothesis Testing Results

Hypothesis Beta t-statistics p-value f² Effect Size Result
H1: FM→PSU 0.514 13.462 < 0.001 0.360 Large Supported
H2: FM→PSE 0.272 5.683 < 0.001 0.080 Small Supported
H3: FM→PB 0.341 7.472 < 0.001 0.132 Small Supported
H4: FM→PR 0.381 8.664 < 0.001 0.170 Medium Supported
H5: FM→SE 0.354 7.721 < 0.001 0.143 Small Supported
H6: FM→CTA 0.180 3.222 0.001 0.033 Small Supported
H7: PSU→INT 0.197 3.589 < 0.001 0.044 Small Supported

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