We revisit the spread of COVID-19 in New Zealand in early 2020.
The object is to apply the exercise below to the current 2021 Delta outbreak in New Zealand.
To estimate the total number of cases, we first have to consider when we may have reached the midpoint.
Even if the midpoint is assessed accurately, it is not just a matter of doubling the number of cases to estimate the total number of cases:
- The number of cases usually declines far slower than they have risen
- There is often a very long tail- at least add 10% for the tail alone
Let’s look at the spread in NZ in 2020. You may like to use a sheet of A4 paper to cover at least the bottom half of your screen (and scroll down the screen) to cover future cases as you look at the graphs (so that you are seeing the data day by day).
The object is to apply this exercise to the current outbreak. How many cases do you think there will be in this 2021 outbreak?
Try not to look ahead- Try to look at one day at a time as if you were there at the time.
First lets look at this graph:
Do you think we have reached the midpoint? How many cases do you think there will be?
The PDFs below are also for 2020 (not the 2021 Delta variant).
This pdf has one more day:
Is your estimate still the same?
The cases continue:
What is your estimate now?
Remember a graph may have more than one peak.
The cases continue:
How good were your estimates?
Where do you think the midpoint actually is?
Here are two other versions of the graph:
Where do you now think the midpoint actually is?
How many cases did you think there would be in the 2020 outbreak in New Zealand?
How accurate were your estimates?
How much did you include for a slow decline in case numbers after the midpoint?
How much extra did you include for a long tail?
How many cases do you now think there will be in the current 2021 Delta outbreak in New Zealand?
Do you think we will have 90 new cases or more on at least one day in New Zealand in 2021?
In the next week?
Do you think we will have at least 1500 cases in the current outbreak?
How many cases do you think we will have?
Note on 24 August 2021 the total number of cases was 148 cases.