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Re: statistical help

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Mon, 26 Feb 2018 13:22:04 -0500

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 ``` More or less the same results as Matt - 95% CI upper limit every ~5months. More important though is what we can expect to occur, which is every 30 days during the school year. Source: https://en.wikipedia.org/wiki/List_of_school_ shootings_in_the_United_States Mass shooting definition: shooting resulting in at least 3 victims, excluding the perpetrator (per definition of the Investigative Assistance for Violent Crimes Act of 2012, signed into law on Jan 2013) SPC T chart of days between mass school shootings (n=121), last 100 years (Upper Control Limit = 3SD); not adjusted for population growth or seasonality; CL = average of 1 every 113 days [image: Inline image 1] The most recent period of stability goes back from event #86 in the figure above, starting at the beginning of 2013 until the current date. This time period makes a new T chart below, which is stable (no significant change) by all special cause rules (1 point >3SD from the center line, 9 points in a row on same side of center line, 6 points in a row all increasing or decreasing, 2 of 3 points >2 SD on same side from CL, 3 of 4 points >1 SD on same side of CL). Now, there is 1 every 41 days, with 3SD UCL of 271 days; not adjusted for seasonality, population growth, or transformed for normality). To the original question of 95% CI question, the UCL for 2 SD is 170 days. The good news is that this is a stable process, so the effect of interventions could be associated with changes in the outcomes. The bad news is that this is a stable process. [image: Inline image 7] But kids are in school seasonally - with decreases seen in spring break and summer. So when school's in session, it's probably more like one mass shooting every 30 days. [image: Inline image 3] If you expand the criteria from school mass shooting to any school shooting (at least 1 injury or death), January is the most frequent month for any school shooting. [image: Inline image 4] Implications: Mass shooter drills in September? Increase mental health resources/screenings in schools/staff/communities after winter break? Other ideas with likely bipartisan support? Long road ahead... Paul Paul Mullan, MD, MPH Director of Research and Quality Improvement, Division of Emergency Medicine Children's Hospital of the King's Daughters Associate Professor, Eastern Virginia Medical School Cell: (713) 855-4827. Office: (757) 668-9220 [log in to unmask] For more information, send mail to [log in to unmask] with the message: info PED-EM-L The URL for the PED-EM-L Web Page is:                  http://listserv.brown.edu/ped-em-l.html ```