Relax? Not yet

Written on 18 April 2020, 07:45pm

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My view on the recent study arguing that the lock-down measures implemented in Belgium should be relaxed to match the ones in the Netherlands, which lead to similar infection numbers. For completion, the 3 main differences between the two countries are:

  • no legal enforcement of the lock-down in the NL
  • all shops remain open in the NL
  • telework is encouraged, but not mandatory in the NL

Note: For the sake of readability, I will add the relevant links at the end of the post.

What I liked in the study

  • the dependency between the policy, human behavior and outcome
  • the use of Google mobility data

The two premises

  • I pretty much agree with the first one – about the complexity of the epidemic models and the fact that the Belgian government is not very transparent in sharing all the data. But we should not underestimate the importance of the scientists working together with the decision-makers.
  • However, I do not agree with the second premise: that the models need precise data in order to work. Scientists routinely work with incomplete or imperfect data. Confidence intervals, margins of error, type I and II errors are all part of the game. This is not a perfect world.

EPSO/AST/133/14 competition

Written on 3 February 2015, 03:32pm

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Because the Notice of Competition and the official comments on the blog are not very clear, here is a visual representation of the competition steps:
AST ICT 133 flow chart
Made with SchemeIt

Talent screener works in 2 stages:
– first a score is calculated based solely on the yes/no answers
– second a score is calculated based on weighted average (each criteria has a number of points assigned).
Like that (note – the talent screener questions below refer to an old competition):
talent screener stages

There, I fixed it.

Amazon interview question

Written on 15 February 2014, 12:18am

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From Stack Exchange:

• 50% of all people who receive a first interview receive a second interview
• 95% of your friends that got a second interview felt they had a good first interview
• 75% of your friends that DID NOT get a second interview felt they had a good first interview
If you feel that you had a good first interview, what is the probability you will receive a second interview?

The easiest way (at least for me) to go is to turn those percentages into some real numbers. For instance:
– 100 friends that got a second interview; 95 of them felt that they had a good first interview
– 100 friends that did NOT get a second interview; 75 of them felt that they had a good first interview.
Now, if you ignore the fact that it’s pretty difficult to have 200 friends (let alone the fact that they all applied for a job at Amazon 🙂 ), the numbers say that:
– 95 + 75 = 170 friends had a good feeling after the first interview
– but only 95 of them had a second interview
– so the probability of you having a second interview is 95 / 170 = 0.558.
In other words, if you felt good after the first interview, you have more than 50% chances that you get a second interview.


Now, if you come up with the answer 55.8% to your Amazon interviewer, I think you would get some points. But not all of them. Because in the logic below there are 2 hidden assumptions: