I pulled this up from the MIT Open CourseWare page under their Problem Solving class. I think they use problems of this caliber to prepare for the Putnam exam.
I wonder if we as a class could take on this one...
3. An unfair coin (probability p of showing heads) is tossed n times. What
is the probability that the number of heads will be even?
That's a great idea. First, try it for specific values of n. If n=1, then the number of heads is even if it's 0, so P(even) = 1-p. If n=2, you could have 0 or 2 heads, so P(even) = (1-p)^2 +p^2 = 1-2p. Obviously there's going to be some kind of binomial identity, but what?
OK, I now know two ways to solve this. The first way was along the lines you described in the break to me, Sam. It makes more sense than I originally thought, and with your Discrete Math knowhow you might be able to solve it.
There's also a clever way, which I admit I didn't figure out until I solved it the other way.
The rising stature of statisticians, who can earn $125,000 at top companies in their first year after getting a doctorate, is a byproduct of the recent explosion of digital data. In field after field, computing and the Web are creating new realms of data to explore - sensor signals, surveillance tapes, social network chatter, public records and more. And the digital data surge only promises to accelerate, rising fivefold by 2012, according to a projection by IDC, a research firm.
When baseball dubbed shortstop Harold Reese "Pee Wee" and first basemen Fred Merkle "Bonehead," they probably weren't trying to lengthen the players' lives. But according to researchers at Wayne State University, major-league players who have nicknames live 2½ years longer, on average, than those without them.
The nickname findings are part of the wide-ranging and often arcane academic research that deals with the national pastime. In another study, we learn that players whose first or last name begins with "K" strike out more than those without "K" initials. And in case you were wondering, research finds Democrats support the designated-hitter rule more than Republicans.
I have no Erdos number as I have not published any joint papers. Also, I'm offended with the slander against Kevin Bacon as a "not too well known American actor." Have you ever heard of Footloose?
Bertrand's Paradox is a question in continuous probability that shows the perils of uniformly distributed variables. The question is simple: given a random chord in a circle, what's the probability that it's longer than the side length of an equilateral triangle inscribed in that circle?