# What Went Wrong? Predictors of Contact Tracing Adoption in Italy during COVID-19 Pandemic
## 3 Results  
### Univariate Analysis for Immuni Adoption  
Of the 501 respondents, 329 reported using Immuni, while 172 did not download the application. Thus, in our sample, the adoption of Immuni appeared to be much higher than in the general Italian population (17.3%, see Table 1). Most of the participants had a high-school diploma (41.5%), Master's Degree (26.3%), and income between EUR 10 k and EUR 40 k per year (50.5%) or lower than EUR 10 k (35.7%). For a more detailed description of the sample, see Table 2.  
First, we analyzed univariate differences between Immuni users (or not) and continuous variables to test whether these two populations differed in terms of Immuni perceived efficacy (H2), risk perception and fear level (H4), attitudes towards the Immuni application (H5), and trust in government and its action to deal with the pandemic (H6). For continuous variables, we relied on [PERSON]'s t-test and assessed the related effect size through [PERSON]'s d (Table 1). A commonly used rule for [PERSON]'s d interpretation identified small, medium, and large effect sizes for d values of 0.2, 0.5, and 0.8, respectively [55]. Nonetheless, this rule should not be interpreted rigidly [56]. Since the fear dimension of the ATCTS scale was not normally distributed, the variable was log-transformed to proceed with our parametric inferential analyses. The analysis highlighted that Immuni adoption is largely related to the perceived efficacy of CT systems and both components of people's attitudes toward CT systems (i.e., fear and acceptance). The participants that downloaded and used the Immuni application also had higher scores on trust in government and its actions against COVID-19, risk perception (Perceived Severity and Likelihood of Infection), and experienced more fear compared to individuals that did not adopt the app. No differences were found regarding participants' age (t\({}_{\text{323.22}}\))= \(-0.56\); \(p\) = 0.58). For categorical variables, [PERSON]'s Chi-square was used to test the association of these variables with Immuni adoption. To define the effect size of each of these characteristics, we relied on Phi coefficients as a measure for the strength of an association between two categorical variables in a 2 \(\times\) 2 contingency table. It was calculated by taking the chi-square value, dividing it by the sample size, and then taking the square root of this value. The Phi coefficient can be interpreted as very strong, strong, moderate, and weak for phi values of 0.25, 0.15, 0.10, and 0.05, respectively ([PERSON], 2017). From the analysis, it emerged that 70.2% of Immuni adopters have at least one family member who used the application. Conversely, just 24.4% of the participants did not use the Immuni application despite one or more members of the family adopting it (\(\chi^{2}_{\text{(1)}}\) = 95.52; \(p\). \(<\) 0.001; \(\Phi\) = 0.44; \(p\). \(<\) 0.001). A similar result emerged, considering whether or not a friend downloaded and used Immuni. The participants who used the CT app reported having at least one friend who did the same in 61.7% of cases. At the same time, 73.8% of Immuni non-adopters revealed not having a friend who used the application (\(\chi^{2}_{\text{(1)}}\) = 57.07; \(p\). \(<\) 0.001; \(\Phi\) = 0.34; \(p\). \(<\) 0.001). Finally, those who reported having at least one acquaintance who used Immuni passed from 16.9% in those who did not adopt Immuni to 35.3% in those who instead adopted it (\(\chi^{2}_{\text{(1)}}\) = 18.59; \(p\). \(<\) 0.001; \(\Phi\) = 0.19; \(p\). \(<\) 0.001). No statistically significant associations were found with participants' gender (\(\chi^{2}_{\text{(1)}}\) = 0.40; \(p\). \(=\) 0.53), education level (\(\chi^{2}_{\text{(5)}}\) = 10.86; \(p\). \(=\) 0.06), occupation (\(\chi^{2}_{\text{(6)}}\) = 8.94; \(p\). \(=\) 0.18), or income (\(\chi^{2}_{\text{(4)}}\) = 2.17; \(p\). = 0.70). Thus, among categorical variables, the strongest association related to the adoption of Immuni appeared to be having a family member who used it, followed