2.1. Study Design

This is a cohort study using a retrospective design over a 12-month period using records from December 2019 to December 2020.

Retrospective cohort studies allow researchers to formulate ideas about the associations and potential relationships between the independent variable (e.g., PACER) and dependent variables (involuntary detentions, hospital diversions) without determining causal effect [48,49,50,51].

There are several strengths to retrospective cohort studies. These include large sample sizes and statistical power based on the availability of large databases of data which have already been collected [48,49,50,51]. Furthermore, both prospective and retrospective cohort studies have high accuracy and efficacy as their main advantages [48,49,50,51]. A primary feature of observational studies is the identification of participants and their exposure to a risk factor, intervention, or outcome, and this is assessed at the study’s starting point [49].

This study will use PACER as the exposure, and police and ambulance cohorts as comparison.