Posted by DaveToo
(here)
Posted by Matthew
(here)
I've come to understand the number of cases is related to the number of tests done. Does anyone know or thought about this too?: the cases rate should be per 100,000 tests done or something like that/ Instead the more tests done the more positive test results (cases)
but we don't see the number of tests done with a false result, just the total positive cases. Or am I missing something. I've got a feeling I might be missing something or got this wrong. Can anyone help confirm or correct?

I've come to understand the number of cases is related to the number of tests done
Not really.
I used to think along those lines too. The past couple of days I decided to do a bit of a deep dive into this with data that is readily available.
First of all to clarify some things you said.
There is not always a direct relation between the number of cases and the number of tests.
Sometimes the more tests you do at a location the number of cases will increase, but sometimes people are just getting tested "to be safe", they have no symptoms. So these people will usually test negative.
Or to put it another way, one day there may be 10 cases in 100 tests at a center, another day
there may be 12 cases in 300 tests at a center etc. etc.
We do know the number of tests with negative results.
We have the following data available to us for each country:
Number of tests/day.
Number of cases/day.
From those two figures we quickly get the number of negative tests/day (Tests - Cases = Negative tests).
I put together a bunch of charts for various countries and also a table of data that reveals something quite interesting.
Canada's tests/case ratio is 21.4
This means for each positive case detected, 21.4 tests are conducted.
United States' tests/case ratio is 12.1
This means for each positive case detected, 12.1 tests are conducted.
So what does this tell us? It depends on how you want to interpret it.
You could say the U.S. is more efficient with its testing. They use fewer tests to find each 'Covid case'.
But every region, city, country is different. Some countries test mainly sick people. Other countries tests any warm body that shows up to be tested.
For those countries that test mainly sick people you would expect a lower tests/case ratio.
Have a look at this table for some numbers you might be surprised seeing.