Calling all Nerds

[wiegie]

If you assume a geometric distribution, the expected value is not (1-p)/p but it is in fact E(N) = 1/p leaving you with an expected value of 10, very close to my crude methodology answer of 9.96.

 

The variance is the same however.

 

(1-p)/p is the expected value of consecutive failures, not the success expected value

 

http://en.wikipedia.org/wiki/Geometric_distribution

 

OK--I think it makes sense then. We expect to have 9 failures (which is what my formula gives) before the success is expected to happen on the 10th try (which is what your formula gives). (I should have paid more attention to what I was answering.)

Edited February 28, 2007 by wiegie

[Controller]

Thanks to all who contributed to this thread.

 

I still don't understand it completely; it will probably come to me at 3 AM or so.

[muck]

otherwise known as clubfoothead's parachute theory of statistics.

 

 

A truly GREAT answer!

[Controller]

The official answer per the prof. was:

 

E[N] = 10

 

and

 

V[N] = 90

 

so, Tford and the Wiegester are on top of their games. Thank you, kind sirs.

 

Oh, and yours truly was the only student to get both answers correct! Who says the huddle membership aint worth the price of admission?

[wiegie]

The official answer per the prof. was:

 

E[N] = 10

 

and

 

V[N] = 90

 

so, Tford and the Wiegester are on top of their games. Thank you, kind sirs.

 

Oh, and yours truly was the only student to get both answers correct! Who says the huddle membership aint worth the price of admission?

 

uh--I thought you had already gotten these questions corrected. I didn't know we were helping you cheat.

[Controller]

uh--I thought you had already gotten these questions corrected. I didn't know we were helping you cheat.

 

 

Not at all - this was an extra credit assignment and you were helping me understand it.

 

When we got to class last night, he had inadvertently left the answer for the E[N] part of the problem written on the whiteboard. Several students quickly wrote it down and attempted to turn it in for partial credit.

 

He asked each of us that turned in an answer to explain how they got it.

 

I was the only one who could explain it and the only one who got full credit. Had it not been for the help received here, I would not have been able to understand it and/or explain it.

 

So, thank you.

[Tford]

Sorry to hijack the thread but;

 

Wiegie, what do you do for a living? Just curious as you seem to have a solid feel for stats.

 

As you probably assumed already I am an engineer.

[Ursa Majoris]

Sorry to hijack the thread but;

 

Wiegie, what do you do for a living? Just curious as you seem to have a solid feel for stats.

 

As you probably assumed already I am an engineer.

 

Wiegie is the nom de plume that the Chairman of the Federal Reserve (a noted FF fan) uses when he's hanging out at the Huddle.

[wiegie]

Wiegie, what do you do for a living? Just curious as you seem to have a solid feel for stats.

 

I'm an economics professor.

[Big Country]

I'm an economics professor.

 

 

I've met wiegie. The experience was . The :beer: was cold. For some reason he has not come back to California, or, if he has, he hasn't let us know ahead of time.

[Ursa Majoris]

I've met wiegie. The experience was . The :beer: was cold. For some reason he has not come back to California, or, if he has, he hasn't let us know ahead of time.

 

cough:cattleprod:cough

[TimC]

Calling all Nerds