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.

Image: HollywoodReporter.com

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:
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Is this the new rocket science? These guys are however closer to infinity than anyone can ever be…
http://techcrunch.com/2013/01/19/your-database-is-probably-terrible/
http://www.wired.com/wiredenterprise/2012/11/google-spanner-time/
http://gigaom.com/2011/12/06/facebook-shares-some-secrets-on-making-mysql-scale/
http://www.computerworld.com/s/article/9225999/Twitter_releases_its_MySQL_scalability_tweaks
http://highscalability.com/blog/2010/5/17/7-lessons-learned-while-building-reddit-to-270-million-page.html

Here is a short story about Tanita Weightcheckers and how NOT to provide a service:
– in the first days of January 2013 I bought a Tanita BC543 scale. It also came with a companion iOS app where you could save your data
– I used the scale + app on a regular basis (2-3 times/week) to track my measurements and improve my shape
– I also used the web interface (weightcheckers.com) to have a better view of the graphs

– Now comes the ‘fun’ part: starting February 6th 2014, the iOS app is no longer working, the website redirects to an online store for scales, and, worst of all, all the measurement data is gone

– I contacted the customer service via Twitter, the contact form and phone. They confirmed me by phone that all the data is deleted, and the iOS app is gone.
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