You have 100 marbles – 50 of them are black and 50 of them are white. You also have 2 brown paper bags.  You can distribute the marbles however you’d like between the two brown paper bags. After you put all the marbles in the bags, you will close your eyes and I will hold the bags behind my back, one in each hand. 

First you must choose an arm and I will present you with the bag that was being held by that arm.  Then you must reach into that bag without looking and choose a marble.

How would you distribute the marbles between the two bags in order to maximize your chances of choosing a black marble?

As I was driving this weekend with my brother and sister-in-law, we were discussing the questions we ask people during interviews.  I generally take the approach of telling people what skills are required for the job and then tacitly suggest that they use their past experiences to show that they qualify.  On the other end of the spectrum, my sister-in-law asks job applicants the brain teaser copied at the top of this entry.

What do these sorts of cognitive questions (like the one above) really tell you about a job applicant?  Does it tell you how they think? Can it tell you if they would be a good candidate for the job? Maybe it just tells you that they’ve been studying case questions that are commonly asked in interviews?

What do you think?

Hint for the brain teaser: the correct distribution of marbles will yield a probability of choosing a black marble that is just a hair under 75%

What do you ask in interviews?