Active Shooter - NYPD Shield

The NYPD chose to restrict quantitative analysis to cases that took place within the
United States because the NYPD limited its internet searches to English-language sites,
creating a strong sampling bias against international incidents. Table 4 presents the
number of cases in the Compendium by country.
Table 4: Number of Incidents by Country
Country Number of Incidents Country Number of Incidents
U.S. 271 Bosnia 1
Canada 8 Brazil 1
Germany 7 Denmark 1
Australia 5 Egypt 1
Israel 3 Greece 1
United Kingdom 4 Norway 1
Finland 2 Slovakia 1
France 2 Somalia 1
India 2 South Korea 1
Italy 2 Spain 1
The Netherlands 2 Sweden 1
Argentina 1 Thailand 1
Austria 1 Yemen 1
Belgium 1
The NYPD chose to restrict quantitative analysis to cases with one or more documented
casualties to compensate for a strong sampling bias. Although the NYPD identified in
the Compendium 40 foiled attacks and three attacks resulting in zero casualties, this
portion of the Compendium is not comprehensive, given the comparatively limited
amount of news coverage these attacks received. 11
As a general rule, the ability to make generalizations regarding a group of events
improves as the number of events in the sample increases. Accordingly, it is difficult to
make precise statistical judgments with limited data. For this reason, many research
questions that would have been interesting to investigate, such as the average number of
deaths in active shooter incidents in each state, cannot be answered with this data set.
11 Incidents in which the attacker was the only casualty may also suffer from limited news reporting,
making this portion of the data set incomplete.
11