It is difficult to say with certainty why respondents to the Facebook survey dropped out at these points, but the partial data on reported conflict exposure suggest that dropout varied with experience of conflict events (see Table 3). We focus on respondents from Gaza for all analysis of reported conflict exposure because only Gazan respondents were asked these questions in the PPCS, but the pattern of results reported in Table 3 is not different if we use the full national sample. Among respondents from Gaza, respondents who reported no exposure to conflict events were overrepresented among those who dropped out of the survey after partially completing it. This pattern is even more pronounced among respondents who dropped out of the survey immediately after the conflict exposure module. Overall, respondents from Gaza who reported experiencing at least one conflict event were about 6.5 percent more likely to complete the survey than those who did not report experiencing any conflict events, which is consistent with hypothesis H1a.

# **Table 3: Respondents who reported no exposure to conflict events were overrepresented among those who dropped out of the Facebook survey**

||**Respondents who reported no**<br>**exposure to conflict events**|
|---|---|
|_Share of all respondents_|37.6%|
|_Share of respondents who dropped out at any time before_<br>_completing the survey_|40.5%|
|_Share of respondents who dropped out at the end of the conflict_<br>_exposure module_|46.0%|

Note: Restricted to respondents from Gaza who answered at least one conflict exposure question.

Were people more willing to provide answers to sensitive questions in the Facebook survey than in the PPCS?

Systematic variations in response patterns may also have contributed to the differences between the PPCS and Facebook survey estimates. One potential variation of this type is sensitivity bias, which could stem from multiple sources.<sup>6</sup> For example, respondents might underreport aggressive tendencies because these tendencies conflict with their self-image, because they fear the consequences if their reporting is disclosed, or because they do not wish to be associated with a socially undesirable trait. They may underreport signs of risk for mental health problems for fear of disclosure or perception of social undesirability, or because mental health problems are considered taboo topics that should not be discussed with others. For the core topics shared between the PPCS and the Facebook survey, we would generally expect response options indicating more severe outcomes to be more sensitive.

Existing evidence suggests that self-administered internet surveys may reflect lower sensitivity bias relative to in-person and telephone surveys, which could be consistent with the pattern of more severe outcomes estimated from the Facebook survey relative to the PPCS. For example, Kreuter et al (2008) found that online self-administration increased accurate reporting of sensitive information relative to computer-assisted telephone interviewing, and Tandon and Vishwanath (2022) presented evidence that anonymous internet-based surveys elicited sensitive information more accurately than a concurrent mobile phone survey. Under the social reference theory developed by Blair et al (2020), self-

> 6 Primarily based on the sources of sensitivity described in Blair et al (2020) and Isaqzadeh et al (2020).

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