There are other announcements after describing the September program so read on to the end.

This program will be presented by either Patrick Ball or Megan Price from the Human Rights Data Analysis Group (HRDAG).

Abstract: Data about mass violence can seem to offer insights into patterns: is violence getting better, or worse, over time? Is violence directed more against men or women? But in human rights data collection, we (usually) dont know what we dont know --- and worse, what we dont know is likely to be systematically different from what we do know.

This talk will explore the assumption that nearly every project using data must make: that the data are representative of reality in the world. We will explore how, contrary to the standard assumption, statistical patterns in raw data tend to be quite different than patterns in the world. Statistical patterns in data tend to reflect how the data were collected rather than changes in the real-world phenomena data purport to represent.

Using analyses of killings in Iraq, homicides committed by police in the US, killings in the conflict in Syria, and homicides in Colombia, we will contrast patterns in raw data with estimates of total patterns of violencewhere the estimates correct for heterogeneous underreporting. The talk will show how biases in raw data can be addressed through estimation, and explain why it matters.

Bio: Patrick Ball has spent twenty-five years building databases and conducting quantitative analysis for nine truth commissions, many non-governmental organizations, and United Nations missions in El Salvador, Ethiopia, Guatemala, Haiti, South Africa, Chad, Sri Lanka, East Timor, Sierra Leone, South Africa, Kosovo, Liberia, Per, Colombia, the Democratic Republic of Congo, and Syria. He has provided expert testimony in the trials of three former heads of state -- Slobodan Miloevi, Efran Ros Montt, and Hissne Habr -- for war crimes, crimes against humanity, and genocide. He co-founded the non-profit [Human Rights Data Analysis Group](https://hrdag.org). These days he hacks mostly in python and R, but bash is always the first cut (-d ' '). He thinks strings are not byte arrays.

Upcoming events: Hadley Wickham of ggplot2 fame will be the presenter at our November meetup on November 17th, also at the New School.

Many thanks to Analytics8 who will be providing refreshments at the September meetup.

Strata + Hadoop World, happening September 26-29 is where cutting-edge science and new business fundamentals intersectand merge. It's a deep dive into emerging techniques and technologies. You'll dissect case studies, develop new skills through in-depth tutorials, share emerging best practices in data science, and imagine the future. Save 20% with discount code PCDVZSF20. Check out the impressive agenda and speaker lineup.
http://www.oreilly.com/pub/cpc/20639