Editing Prevalence (section)

===Period prevalence===
'''Period prevalence'''<!--Redirects here, bolded per MOS:BOLD--> is the proportion of the population with a given disease or condition over a specific period of time. It could describe how many people in a population had a cold over the cold season in 2006, for example.{{cn|date=May 2023}} It is expressed as a percentage of the population and can be described by the following formula:

Period prevalence (proportion) = Number of cases that existed in a given period ÷ Number of people in the population during this period{{citation needed|date=June 2022}}

The relationship between incidence (rate), point prevalence (ratio) and period prevalence (ratio) is easily explained via an analogy with photography. Point prevalence is akin to a flashlit photograph: what is happening at this instant frozen in time. Period prevalence is analogous to a long exposure (seconds, rather than an instant) photograph: the number of events recorded in the photo whilst the camera shutter was open. In a movie each frame records an instant (point prevalence); by looking from frame to frame one notices new events (incident events) and can relate the number of such events to a period (number of frames); see [[Incidence (epidemiology)|incidence rate]].{{citation needed|date=June 2022}}