Optimizing Diagnosis: Unmasking the Effectiveness of Dual Viral Testing

Image by the author. It is just a descriptive picture. The accuracy of the tests below is separate from Flowflex ones.

I have taken the problem statement from a mathematician, Boris Trushin’s youtube channel → https://youtu.be/8TBib_RSE5g (the video is in Russian, subtitles n/a, but the language of numbers is international)

This article is behind a paywall. To bypass it, please open this pinned article with friend links inside.

Intro

I got the idea for the article a month ago by visiting the first Dutch lesson at the school for adults. I had a cold then but could not miss the class because of the social contract with the Belgian government. After an explanation of the situation to the school’s staff, I received three COVID tests and took my way back home.

• Why did they give me three COVID tests? Was it for my wife and me?
• Or was it to test myself for several days?
• Or were they good at probability theory?

I do not know for sure.
I took the test twice (but why?) and received negative results in both cases. Ultimately, it was just the flu, and I fully recovered in four days.
What was the probability I would be ill if the test were positive? And how did the probability change if the second test also were positive? Let’s try to study it.