Interview Question for Analyst at Argus Information & Advisory Services:

Feb 22, 2010

1 in base (Traffic Lights in Manhattan)

Sure, it's cheating, but the question is absurd. Ask a silly question, get a silly answer.

3. Red, Yellow and Green

Let X be the number of blocks west to east.
Let Y be the number of blocks south to north.
   then X * Y = the number of traffic lights.

0, they use traffic cops!

Q: How many traffic signals are there in New York City?
A: As of January 2006, there were 11,871 signalized intersections Citywide, including 2,795 in Manhattan, 4,100 in Brooklyn, 2,942 in Queens, 1,536 in the Bronx, and 500 in Staten Island.

http://www.nyc.gov/html/dot/html/faqs/faqs_signals.shtml

Q: How many traffic signals are there in New York City?
A: Not enough, traffic there is terrible.

Sounds like your standard estimation problem, along the lines of: how many basketballs will fit in this room, how many piano tuners are there in America, and how many gas stations are there in America?

All designed to see how you come up with best guesses, how logical your thought patterns are, etc. (I've been asked the last two - I must have done well, because I got the job).

I had ballparked 225 blocks and 12 avenues...225*12=2700. googline the answer gave me:

A: As of January 2006, there were 11,871 signalized intersections Citywide, including 2,795 in Manhattan, 4,100 in Brooklyn, 2,942 in Queens, 1,536 in the Bronx, and 500 in Staten Island.

http://www.nyc.gov/html/dot/html/faqs/faqs_signals.shtml

so i was pretty close!

I got the similar one "How many registered cars are there in your town?" Obviously not knowing, I went about it like so:
1) Go to the DMV and find out .
2a) If that information isn't directly connected, I find out how many registered cars are there in my state, then took the names and cross-referenced them with people who live in my town.
2b) I also made sure to include that some people live in the county but live in-between towns. I find out what is considered "within city limits" and "not within city limits", and added those people within.
3) If that information isn't available, I estimate using (2b) above with "How many cars on average does a person register in Dayton", then multiplied, adding some +/-%.

May have over-analyzed, but I wanted to show how to get the direct answer, then what options you use when you don't have it.

good probability that the answer includes a fraction due to boundary lines

As many as needed plus 10% because city government is involved.