Sampling > Extreme Case Sampling

## What is Extreme Case Sampling?

Extreme Case Sampling focuses on participants with unique or special characteristics. An extreme case (or deviant case) can be thought of as an outlier — an observation that takes on an extremely high or extremely low value. The general idea is that **if you study extremes of the population, it could garner some valuable insights that can be generalized to the population as a whole.** For example, if you were studying inner city violence, you could study a city with high violence and compare it to a city with low violence.

Like any sampling technique where a researcher deliberately chooses cases, extreme case sampling could result in selection bias, undermining results (Collier & Mahoney, 1996). Selection bias can largely be avoided if extreme cases from both ends of the spectrum are considered along with the general population as a whole.

## Examples

- Angela Browne studied
*male*victims of domestic violence for her book “When Battered Women Kill.” - Kristen Monroe studied a variety of unusual altruists for her book “The Heart of Altruism.” They included a poetry editor who — armed with a cane — saved a young girl from being raped, and Otto Schindler, the German businessman who saved over a hundred Jews.
- Benjamin Reilly’s work on studying democracy and eloctoral systems focused on unusual societies like Papua New Guinea, a country of “exceptional ethnic fragmentation” which has thousands of ethnic “micropolities” speaking 840 languages.
- Frederic Deyo (1987) studied East Asian NICs (Newly Industrialized Countries), which stood “in stark contrast” to other Third World countries.

## Quantifying Extreme Cases

Gerring (2006) defines extreme cases by their z-scores — although this only works with normally distributed cases. Cases with large World Politics. Vol 49, Issue 1. October, pp. 56-91.

Deyo, F. (Ed.) (1987). The Political Economy of the New Asian Industrialism. Cornell University Press.

Gerring, J. (2006). Case Study Research: Principles and Practice. Cambridge University PRess.

Monroe, K. (1996). The Heart of Altruism: Perceptions of a Common Humanity. Princeton University Press.

Reilly, B. (2000). Electoral Systems for Divided Societies. Retrieved 1/20/2017 from here: (https://devpolicy.crawford.anu.edu.au/pdf/staff/ben_reilly/ReillyB_04.pdf.)

Tendler (1997)

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