###### 24 July 2021

# Birthday quiz

I’m always up for playing games. I also like to create them. As I mentioned in July’s newsletter, I devised a special birthday quiz with just 9 questions. A number of people submitted answers but alas no one got all the responses right. In fact the best scorer was 7 out of 9. It’s okay, you will be able to have another go next year!

Here are all the questions, so that gives you one more chance to play without looking straight at the answers, added afterwards.

- What does 247 stand for in seb247.com?
- How many years have I worked at Google?
- How many siblings do I have?
- How many people were selected as participants in the Coaching Experiment?
- In which years did my lungs collapse?
- How many citizenships do I have?
- How many countries are represented by stories on seb247.com?
- What are the musical instruments I know how to play?
- Since this is another year of pandemic, let's have a little puzzle on the topic. You'll need to find the solution to the first puzzle to be able to solve the second one. The first puzzle's solution is the line number on which there is an error in the image below. The second puzzle is as follows: if a test to detect a disease whose prevalence is 1/1,000 has a false positive rate of x% where x is the solution to the first puzzle, what is the chance (as in the probability percentage) that a person found to have a positive result actually has the disease?

And here are the answers:

1. 247 stands for 24th July, my birthday. It also corresponds to the reputation that I generally hold of being responsive day and night, 24/7. Check out the FAQ for the same information. Everyone thankfully got that question correct.

2. I joined Google on the 5th of February 2007, so the answer is 14 years. Once again, everyone got that question right.

3. I have 3 siblings, all younger than me (we’re all roughly 2 years apart).

4. Four people – two women and two men – were selected to the Coaching Experiment. Stay tuned for the documentary.

5. The correct years were 2014 and 2017, for a grand total of 3 surgeries.

6. I hold 3 citizenships. No one guessed that question correctly, but I expected this to be the case. I am French by birth, Swiss by naturalisation since March 2021… and European since 1992. That’s right, there is such a thing as a European citizenship. Alas, not many people – including Europeans themselves – know it or feel that way. I wish people understood that sense of unity instead of being stupidly proud of their national citizenships.

7. The answer is 21. The emphasis was on “represented by stories”. Two additional countries are indicated in the timeline but no stories have yet been published for them.

9. The solution to the first puzzle is 5: since a = b, a – b = 0, it’s therefore not possible to hop from line 4 to line 5. The equation on line 4 is still correct, that’s why the answer to the first puzzle is line 5.

The second puzzle’s solution is 1.96%. That’s right: if a test to detect a disease whose prevalence is 1/1,000 has a false positive rate of 5%, there’s only a 1.96% chance that a person found to have a positive result actually has the disease. Here’s the demonstration: let’s randomly pick 1,000 people. Out of those, 1 out of 1,000 will have the disease (prevalence rate of 1/1,000) and will be tested as such. But an additional 50 out of those 1,000 will also see their tests be positive (false positivity rate of 5%). In total, 51 people were tested positive, but only 1 has the disease. The probability of someone tested positive to be actually sick is therefore 1 out of 51, which is approximately 1.96%.

I hope you enjoyed the quiz, or at least learned one (useful) thing or two!