This study explores how researchers’ analytical choices affect the reliability of scientific findings. Most discussions of reliability problems in science focus on systematic biases. We broaden the lens to emphasize the idiosyncrasy of conscious and unconscious decisions that researchers make during data analysis. We coordinated 161 researchers in 73 research teams and observed their research decisions as they used the same data to independently test the same prominent social science hypothesis: that greater immigration reduces support for social policies among the public. In this typical case of social science research, research teams reported both widely diverging numerical findings and substantive conclusions despite identical start conditions. Researchers’ expertise, prior beliefs, and expectations barely predict the wide variation in research outcomes. More than 95% of the total variance in numerical results remains unexplained even after qualitative coding of all identifiable decisions in each team’s workflow. This reveals a universe of uncertainty that remains hidden when considering a single study in isolation. The idiosyncratic nature of how researchers’ results and conclusions varied is a previously underappreciated explanation for why many scientific hypotheses remain contested. These results call for greater epistemic humility and clarity in reporting scientific findings.

Identifying inattentive respondents in self-administered surveys is a challenging goal for survey researchers. Instructed response items (IRIs) provide a measure for inattentiveness in grid questions that is easy to implement. The present article adds to the sparse research on the use and implementation of attention checks by addressing three research objectives. In a first study, we provide evidence that IRIs identify respondents who show an elevated use of straightlining, speeding, item nonresponse, inconsistent answers, and implausible statements throughout a survey. Excluding inattentive respondents, however, did not alter the results of substantive analyses. Our second study suggests that respondents’ inattentiveness partially changes as the context in which they complete the survey changes. In a third study, we present experimental evidence that a mere exposure to an IRI does not negatively or positively affect response behavior within a survey. A critical discussion on using IRI attention checks concludes this article.

Interview duration is an important variable in web surveys because it is a direct measure of the response burden. In this article, we analyze the effects of the survey design, respondent characteristics, and the interaction between these effects on interview duration. For that purpose, we applied multilevel analysis to a data set of 21 web surveys on political attitudes and behavior. Our results showed that factors on both levels, the individual and the survey level, had effects on interview duration. However, the larger share of the variation in interview duration is explained by the characteristics of the respondents. In this respect, we illustrate the impact of mobile devices and panel recruitment on interview duration. In addition, we found important relationships between the respondents' attitudes and how a web survey is designed: Highly motivated respondents spent significantly more time answering cognitively demanding questions than less motivated respondents. When planning a survey, not only the number and formats of questions need to be taken into account but also the expected sample composition and how the participants will respond to the design of the web survey.

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Our study explores the adoption of Facebook and Twitter by candidates in the 2013 German Federal elections. Utilizing data from the German Longitudinal Election Study candidate survey fused with data gathered on the Twitter and Facebook use of candidates, we draw a clear distinction between Facebook and Twitter. We show that adoption of both channels is primarily driven by two factors: party and money. But the impact of each plays out differently for Facebook and Twitter. While the influence of money is homogenous for Facebook and Twitter with the more resources candidates have, the more likely they are to adopt, the effect is stronger for Facebook. Conversely, a party's impact on adoption is heterogeneous across channels, a pattern we suggest is driven by the different audiences Facebook and Twitter attract. We also find candidates' personality traits only correlate with Twitter adoption, but their impact is minimal. Our findings demonstrate that social media adoption by politicians is far from homogenous, and that there is a need to differentiate social media channels from one another when exploring motivations for their use.