# Covid-19 in Canada: What do the Numbers Mean

The Covid-19 pandemic is unique because the virus emerged in a globally connected world. This enabled the virus to spread quickly across the globe. At the same time, the ability to fight the virus has never been better. Chinese scientists quickly developed a test to identify infected individuals. This made it possible to isolate infected individuals and prevent the spread of the virus. It also provided an unprecedented amount of data that are widely shared on websites and in the news about the number of COVID-19 positive cases in different countries, the Canadian provinces. For example, the government of Canada keeps Canadian citizens informed on a website that tracks cases and COVID-19 fatalities.

As a psychologist, I wonder what Canadians are learning from these numbers. When I teach psychology, I spend a lot of time explaining what numbers actually mean. My concerns is that Canadians are bombarded with COVID-19 numbers with little information what these numbers actually mean. Every Canadian with some knowledge about Canada will notice that the numbers are bigger for provinces with a larger population, but few Canadians may know the exact population of provinces and are willing to compute the fatality rates of provinces that take population size into account. So, it remains unclear whether the situation is better or worse in Manitoba or Alberta. A simple solution to this problem would be to provide information about the number of cases for every 100,000 people.

Taking population size into account is a step in the right direction, but there is another problem that makes comparisons of provinces difficult. The number of cases that are detected also depends on the number of tests that are done. Alberta rightfully points out that they are world-leaders in the use of testing to fight the spread of COVID-19. While massive testing is positive, it has the negative effect that Alberta is also likely to find more cases than Ontario, where capacity to test the large population of Ontario is more limited. A solution to this problem is to compute the positive rate; that is the number of positive tests over the number of tests conducted. This also makes it unnecessary to take population size into account. Provinces with a larger population are likely to conduct more tests, but what matters is how many tests are being done, not how many people live in a province. A province with a large population could have a low number of cases, if there is very little testing.