## Tuesday, October 27, 2020

### Statistical Illiteracy

Throughout the Covid-19 Pandemic, numbers and statistics have become part of our lives. We have got used to numbers in a way we never thought possible - nothing right now will make us happier than seeing numbers going down. We should all be able to interpret and understand what the numbers mean.

Carlo Rovelli writes in yesterday's Guardian newspaper: "Statistical illiteracy isn't a niche problem. During a pandemic, it can be fatal" and that "Insufficient understanding of statistics is widespread". Most of us trust our Government to use data in the fairest and wisest way possible. Others use numbers to spread fake news and concoct conspiracy theories. However, as Rovelli says: "Our extensive statistical illiteracy is today particularly dangerous".

Most people understand as least some basic probability. For example, tossing a coin will be 50/50 for heads/tails. No matter how often you toss a coin, you cannot be certain whether the result will be heads or tails. But you know what the probability is.

Numbers don't lie, but statistics involves uncertainty. In my classes we often conducted statistical tests at a 95% confidence level, sometimes 99%. In relation to Covid-19 - if a vaccine was effective for 95% of people in Ireland, that would mean that it would be ineffective for around 50,000 people (1% approx of our population). This has obvious ethical implications. Would you take the chance and get vaccinated with 99% accuracy? How about 99.9%, which would mean that a vaccine would not work for about 5,000 people, or even 99.99% and 500 people losing out? You can see why vaccine trials are so important. No vaccine will be 100% effective. This means that you cannot be 100% certain that you will get infected with the virus, but also that you cannot be 100% certain that you will be safe. So for example, if you reduce your number of contacts, you will reduce the probability of getting the virus, but not by 100%.

Knowing and understanding statistics and probability will help stop the spread of the virus, but remember, not by 100%.