Gary Cornell – Page 6 – A mathematician looks at stuff

A quick comment on the Moderna news: some arithmetic helps with the hype

May 19, 2020 by admn

There was some good (if very preliminary) news from Moderna on their vaccine candidate: https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-positive-interim-phase-1-data-its-mrna-vaccine And yes it does seem to be good news. But leaving aside that they so far only report results for 8 people from their 45 person Phase 1 trial, some 4th grade arithmetic shows that even if (as we all … Read more

Testing 2: Why positive results on very sensitive tests may not mean much

May 19, 2020May 18, 2020 by admn

In a previous blog I said that we say that a test is very sensitive if it has very few false negatives. I then said that if all you know about the test is that it is a very sensitive test, only it’s negative results are truly informative! Getting a positive result i.e. you are … Read more

Completely losing respect for Deborah Brix – A mathematician looks at death rates from Covid 19

May 15, 2020May 13, 2020 by admn

I don’t know if what is mentioned in this article is true: https://www.thedailybeast.com/team-trump-pushes-cdc-to-dial-down-covid-death-counts but if it is, I have completely lost respect for Dr. Deborah Brix (not that I had much before considering her appearances on Fox news defending the indefensible – like Trump’s “musings” about bleach and UV light). The question of how many … Read more

Percentages again: False Negatives (sensitivity) and False Positives (specificity) in testing

May 11, 2020May 10, 2020 by admn

We know testing is all important to get through this. People need to know if they have active virus so they can adjust their behavior accordingly. Anyone who tests positive should self quarantine for 14 days and we also need to do contact tracing to find the people that they have been near to. (I … Read more

Understanding flattening the curve

May 6, 2020May 5, 2020 by admn

I was talking to a couple of people and it became clear that people don’t completely grok what flattening the curve means. If you like it in the form of an aphorism, it means (to quote some unnamed wit): “Look you idiot, flattening the curve doesn’t mean you won’t get sick, it means there will … Read more

Simple Extrapolations, back of envelope calculation, scary number of deaths,

May 12, 2020May 4, 2020 by admn

There are a lot of models of disease transmission out there, I hope to do multiple blog posts on them! But for now I want to point out a simple “back of envelope” calculation may give as good an estimate on the (scary) number of deaths as far more complicated models. All you have to … Read more

What it would take to get me (and I think many other people) on a plane, train or bus

May 27, 2020April 27, 2020 by admn

Not a math related post, just common sense this time. (It is inspired by WHO (which has great scientists if lousy leaders no matter what our both scientifically illiterate and innumerate president says), pointing out there is no evidence yet that having the virus means you would have enough antibodies to prevent another infection. Sure, … Read more

Percentages – it’s all about the base

May 6, 2020April 22, 2020 by admn

You know percentages are funny: it seems to be another one of those things (like exponential growth) where our first instincts are often wrong. The difference is that most people can do the calculations quickly enough so that they won’t persist in believing the wrong thing after you point the mistake out to them. Take … Read more

Multiplication of probabilities – or what to do when you have to go shopping.

May 6, 2020April 21, 2020 by admn

My last blog said “you should stay at home damn it.” Problem is, unless you are a millionaire survivalist, we all have to go out occasionally to the supermarket. So the question is, how can you reduce the odds of catching Covid 19? How can you feel reasonably safe psychologically and in reality? The answer … Read more

The parable of the lily pond-or why you should shelter in place

May 6, 2020April 20, 2020 by admn

Behavioral economists have shown our brains are hard wired to certain ways of thinking that are “wrong” – well at least to people who still seem to believe in “homo economicus”. We seem to have have hard wired ways of thinking, like the “prospect theory” that won Kahneman the Nobel Prize in Economics that shows … Read more