Security and privacy researchers often rely on data collected from Amazon Mechanical Turk (MTurk) to evaluate security tools, to understand users' privacy preferences and to measure online behavior. Yet, little is known about how well Turkers' survey responses and performance on security-and privacy-related tasks generalizes to a broader population. This paper takes a first step toward understanding the generalizability of security and privacy user studies by comparing users' selfreports of their security and privacy knowledge, past experiences, advice sources, and behavior across samples collected using MTurk (n=480), a census-representative web-panel (n=428), and a probabilistic telephone sample (n=3,000) statistically weighted to be accurate within 2.7% of the true prevalence in the U.S. Surprisingly, the results suggest that: (1) MTurk responses regarding security and privacy experiences, advice sources, and knowledge are more representative of the U.S. population than are responses from the census-representative panel; (2) MTurk and general population reports of security and privacy experiences, knowledge, and advice sources are quite similar for respondents who are younger than 50 or who have some college education; and (3) respondents' answers to the survey questions we ask are stable over time and robust to relevant, broadlyreported news events. Further, differences in responses cannot be ameliorated with simple demographic weighting, possibly because MTurk and panel participants have more internet experience compared to their demographic peers. Together, these findings lend tempered support for the generalizability of prior crowdsourced security and privacy user studies; provide context to more accurately interpret the results of such studies; and suggest rich directions for future work to mitigate experiencerather than demographic-related sample biases.

Data science has been growing in prominence across both academia and industry, but there is still little formal consensus about how to teach it. Many people who currently teach data science are practitioners such as computational researchers in academia or data scientists in industry. To understand how these practitioner-instructors pass their knowledge onto novices and how that contrasts with teaching more traditional forms of programming, we interviewed 20 data scientists who teach in settings ranging from small-group workshops to large online courses. We found that: 1) they must empathize with a diverse array of student backgrounds and expectations, 2) they teach technical workflows that integrate authentic practices surrounding code, data, and communication, 3) they face challenges involving authenticity versus abstraction in software setup, finding and curating pedagogically-relevant datasets, and acclimating students to live with uncertainty in data analysis. These findings can point the way toward better tools for data science education and help bring data literacy to more people around the world. CCS CONCEPTS • Social and professional topics → Computing education.

Data scientists often collaborate with clients to analyze data to meet a client's needs. What does the end-to-end workflow of a data scientist's collaboration with clients look like throughout the lifetime of a project? To investigate this question, we interviewed ten data scientists (5 female, 4 male, 1 non-binary) in diverse roles across industry and academia. We discovered that they work with clients in a six-stage outer-loop workflow, which involves 1) laying groundwork by building trust before a project begins, 2) orienting to the constraints of the client's environment, 3) collaboratively framing the problem, 4) bridging the gap between data science and domain expertise, 5) the inner loop of technical data analysis work, 6) counseling to help clients emotionally cope with analysis results. This novel outer-loop workflow contributes to CSCW by expanding the notion of what collaboration means in data science beyond the widely-known inner-loop technical workflow stages of acquiring, cleaning, analyzing, modeling, and visualizing data. We conclude by discussing the implications of our findings for data science education, parallels to design work, and unmet needs for tool development.CCS Concepts: • Human-centered computing → Human computer interaction (HCI).

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Data scientists often collaborate with clients to analyze data to meet a client's needs. What does the end-to-end workflow of a data scientist's collaboration with clients look like throughout the lifetime of a project? To investigate this question, we interviewed ten data scientists (5 female, 4 male, 1 non-binary) in diverse roles across industry and academia. We discovered that they work with clients in a six-stage outer-loop workflow, which involves 1) laying groundwork by building trust before a project begins, 2) orienting to the constraints of the client's environment, 3) collaboratively framing the problem, 4) bridging the gap between data science and domain expertise, 5) the inner loop of technical data analysis work, 6) counseling to help clients emotionally cope with analysis results. This novel outer-loop workflow contributes to CSCW by expanding the notion of what collaboration means in data science beyond the widely-known inner-loop technical workflow stages of acquiring, cleaning, analyzing, modeling, and visualizing data. We conclude by discussing the implications of our findings for data science education, parallels to design work, and unmet needs for tool development.CCS Concepts: • Human-centered computing → Human computer interaction (HCI).