[xg15]

I have seen those studies pop up from time to time on HN with conclusions altering between "it's reachin worrying proportions", "there is an increase", "there is no increase", "they are so rare as to not worth considering".

From what I understand, the decision of what kinds of shootings are included has a large influence on the conclusion - e.g., the "there have been 18 shootings in 2018 so far" articles from a while ago used a comparatively low threshold for inclusion.

The threshold for this study seems to be "4 or more victims", which I think is similar to the threshold official publications used at the beginning of the Obama administration. I believe there were complaints that the threshold is unreasonably high which caused it to be adjusted - however, I don't have any sources for that ready, so if anyone knows more, please correct me.

In any case, it's important to look at the criteria if one wants to compare those studies.

[cliff_hanger]

It's not clear to me why this study would set those thresholds for the underlying data (4+ Victims & 2+ deaths), this seems to downplay the number of incidents. At the very least there should be some explanation of why this limit is in place, as it has a significant impact on the findings.

Closest thing I can find to an accurate data-set is here: https://www.kaggle.com/ecodan/us-school-shootings-dataset/no.... Data seems to be a blend of a northwestern study and the wikipedia list of shootings.

[xg15]

Absolutely. Even if there is some research question by which this criterion would be useful, it doesn't lead the underlying conclusions that school shootings in general are a rare event, declining in frequency.

Interestingly, according to [1], the criterion used by the FBI to assess mass shooting used to be "at least 4 persons killed or wounded" - until it got changed to "at least 3 persons" in 2013. So the criterion the study uses is stricter than both the old and the new way of counting the FBI uses.

Note also that, according to [2], even though the rate of mass shooting at schools seems to be decreasing, the rate of mass shootings in general is increasing.

See also [3] for more information about the different definitions and ways of counting.

[1] https://en.m.wikipedia.org/wiki/Mass_shooting

[2] https://www.fbi.gov/file-repository/active-shooter-study-200...

[3] https://www.theatlantic.com/education/archive/2018/02/anothe...