Tag: prevalence

Prevalence

Posted on by Prav

In the last post we talked briefly about both Incidence and Prevalence.

Quick recap

Prevalence is the number of incidents/cases/chocolate that are already in the population/box of chocolates at that point in time.

Occasionally it is called Point Prevalence. This is to let us know that the prevalence is being measured over a single point if time, versus a period of time (weeks – months)

Period Prevalence – Prevalence measured over weeks/months

Given that prevalence represents a part of a whole group, it can never be more than 1 when expressed as an equation.

Prevalence is basically a useful tool in giving us an initial idea of the extent of a disease/outcome. However if does not tell us how many new cases take place, how often this particular outcome happens, how long the disease/outcome lasts and what the risk factors are.

Given that it is election time that will be my example.

So Blythe Valley typically was a Labour safe seat. And the labour party held a majority based on the last election (point of time). However, this does not take into consideration the new voters who voted Conservative or the people who changed their mind and voted Conservative in this election.

Life is like a box of chocolates – Prevalence vs Incidence

Posted on by Prav

When talking about frequency we consider it in two ways, namely prevalence and incidence.

Prevalence – Is the number of known cases at a given point in time
Incidence – Is the number of new cases in a population over a specified time

Why is this significant? I like to think of it as a box of chocolates.

Out of this box of chocolates that I am using for our Christmas party, my favourite is the purple one – the awesome hazelnut and caramel filled milk chocolate. So my Prevalence in this instance would be all the purple chocolates I have at that particular point of time in said box of chocolates. I do not take into account the amount of chocolates that might be eaten during the Christmas party, gotten rid of because the wrappers were ruined nor do I consider the fact that perhaps some other kind souls would bring me more chocolate to contribute to the sweet bowl. All it tells me is the amount of purple chocolates present out of the 48 chocolates currently available.

My Incidence however, is the hope that some kind soul will bring more chocolates to said party and the potential new purple chocolates that might be added to the sweet bowl. I do not consider the amount of chocolates that have been eaten, those with ripped packaging that have to be put aside or removed cause no one likes them (here’s looking at you coconut cream). I just look at the potential amount of new purple chocolates that might be present over the total number of chocolates in hand.

However there is a lot more to incidence and prevalence and we will discuss it in the next few posts.