How many piano tuners are there in Chicago?

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pages: 317 words: 100,414

Superforecasting: The Art and Science of Prediction by Philip Tetlock, Dan Gardner

Affordable Care Act / Obamacare, Any sufficiently advanced technology is indistinguishable from magic, availability heuristic, Black Swan, butterfly effect, buy and hold, cloud computing, cuban missile crisis, Daniel Kahneman / Amos Tversky, desegregation, drone strike, Edward Lorenz: Chaos theory, forward guidance, Freestyle chess, fundamental attribution error, germ theory of disease, hindsight bias, How many piano tuners are there in Chicago?, index fund, Jane Jacobs, Jeff Bezos, Kenneth Arrow, Laplace demon, longitudinal study, Mikhail Gorbachev, Mohammed Bouazizi, Nash equilibrium, Nate Silver, Nelson Mandela, obamacare, pattern recognition, performance metric, Pierre-Simon Laplace, place-making, placebo effect, prediction markets, quantitative easing, random walk, randomized controlled trial, Richard Feynman, Richard Thaler, Robert Shiller, Robert Shiller, Ronald Reagan, Saturday Night Live, scientific worldview, Silicon Valley, Skype, statistical model, stem cell, Steve Ballmer, Steve Jobs, Steven Pinker, tail risk, the scientific method, The Signal and the Noise by Nate Silver, The Wisdom of Crowds, Thomas Bayes, Watson beat the top human players on Jeopardy!

Now I’ll assemble my guesses to make a final calculation: If 50,000 pianos need tuning once a year, and it takes 2 hours to tune one piano, that’s 100,000 total piano-tuning hours. Divide that by the annual number of hours worked by one piano tuner and you get 62.5 piano tuners in Chicago. So I will estimate that there are sixty-three piano tuners in Chicago. How close am I? Many people have taken a crack at Fermi’s classic puzzler over the years, including the psychologist Daniel Levitin, whose presentation I’ve adapted here.6 Levitin found eighty-three listings for piano tuners in the Chicago yellow pages, but many were duplicates, such as businesses with more than one phone number. So the precise number isn’t certain. But my estimate, which rests on a lot of crude guesswork, looks suprisingly close to the mark.

In fact, no serious analysis of this critical forecast was conducted until 1967—years after the decisions to escalate had been made.4 “The foundations of our decision making were gravely flawed,” McNamara wrote in his autobiography. “We failed to analyze our assumptions critically, then or later.”5 Ultimately, it’s not the crunching power that counts. It’s how you use it. Fermi-ize Here’s a question that definitely was not asked in the forecasting tournament: How many piano tuners are there in Chicago? Don’t even think about letting Google find the answer for you. The Italian American physicist Enrico Fermi—a central figure in the invention of the atomic bomb—concocted this little brainteaser decades before the invention of the Internet. And Fermi’s students did not have the Chicago yellow pages at hand.

Fermi knew people could do much better and the key was to break down the question with more questions like “What would have to be true for this to happen?” Here, we can break the question down by asking, “What information would allow me to answer the question?” So what would we need to know to calculate the number of piano tuners in Chicago? Well, the number of piano tuners depends on how much piano-tuning work there is and how much work it takes to employ one piano tuner. So I could nail this question if I knew four facts: 1. The number of pianos in Chicago 2. How often pianos are tuned each year 3. How long it takes to tune a piano 4.


pages: 685 words: 203,949

The Organized Mind: Thinking Straight in the Age of Information Overload by Daniel J. Levitin

airport security, Albert Einstein, Amazon Mechanical Turk, Anton Chekhov, Bayesian statistics, big-box store, business process, call centre, Claude Shannon: information theory, cloud computing, cognitive bias, complexity theory, computer vision, conceptual framework, correlation does not imply causation, crowdsourcing, cuban missile crisis, Daniel Kahneman / Amos Tversky, delayed gratification, Donald Trump, en.wikipedia.org, epigenetics, Eratosthenes, Exxon Valdez, framing effect, friendly fire, fundamental attribution error, Golden Gate Park, Google Glasses, haute cuisine, How many piano tuners are there in Chicago?, impulse control, index card, indoor plumbing, information retrieval, invention of writing, iterative process, jimmy wales, job satisfaction, Kickstarter, life extension, longitudinal study, meta-analysis, more computing power than Apollo, Network effects, new economy, Nicholas Carr, optical character recognition, Pareto efficiency, pattern recognition, phenotype, placebo effect, pre–internet, profit motive, randomized controlled trial, Rubik’s Cube, shared worldview, Skype, Snapchat, social intelligence, statistical model, Steve Jobs, supply-chain management, the scientific method, The Wealth of Nations by Adam Smith, The Wisdom of Crowds, theory of mind, Thomas Bayes, Turing test, ultimatum game, zero-sum game

“How many Reese’s Peanut Butter Cups would it take to encircle the globe at the equator?” and “How many piano tuners are there in Chicago?” Approximating involves making a series of educated guesses systematically by partitioning the problem into manageable chunks, identifying assumptions, and then using your general knowledge of the world to fill in the blanks. How would you solve the problem of “How many piano tuners are there in Chicago?” Google wants to know how people make sense of the problem—how they divide up the knowns and unknowns systematically. Remember, you can’t simply call the Piano Tuners Union of Chicago and ask; you have to work this from facts (or reasonable guesses) that you can pull out of your head.

In one year, a piano tuner can tune 1,000 pianos (2,000 hours per year ÷ 2 hours per piano). It would take 50 tuners to tune 50,000 pianos (50,000 pianos ÷ 1,000 pianos tuned by each piano tuner). Add 15% to that number to account for travel time, meaning that there are approximately 58 piano tuners in Chicago. What is the real answer? The Yellow Pages for Chicago lists 83. This includes some duplicates (businesses with more than one phone number are listed twice), and the category includes piano and organ technicians who are not tuners. Deduct 25 for these anomalies, and an estimate of 58 appears to be very close.


pages: 407 words: 90,238

Stealing Fire: How Silicon Valley, the Navy SEALs, and Maverick Scientists Are Revolutionizing the Way We Live and Work by Steven Kotler, Jamie Wheal

3D printing, Alexander Shulgin, augmented reality, Berlin Wall, Bernie Sanders, bitcoin, blockchain, Burning Man, Colonization of Mars, crowdsourcing, David Brooks, delayed gratification, disruptive innovation, Electric Kool-Aid Acid Test, Elon Musk, en.wikipedia.org, high batting average, hive mind, How many piano tuners are there in Chicago?, Hyperloop, impulse control, independent contractor, informal economy, Jaron Lanier, John Markoff, Kevin Kelly, lateral thinking, Mason jar, Maui Hawaii, McMansion, means of production, Menlo Park, meta-analysis, music of the spheres, pattern recognition, Peter Thiel, PIHKAL and TIHKAL, prosperity theology / prosperity gospel / gospel of success, Ray Kurzweil, ride hailing / ride sharing, risk tolerance, science of happiness, selective serotonin reuptake inhibitor (SSRI), Silicon Valley, Silicon Valley startup, Skype, Steve Jobs, Tony Hsieh, urban planning

These days, they’ll just get trolled online, then ignored. And what that does is leave more room for open experimentation. It disempowers anyone tempted to escalate his position and privilege, and empowers everyone else to make sense of their own experiences. When the physicist Enrico Fermi famously guessed the number of piano tuners in Chicago, or the number of stars in our galaxy, he did so by applying provisional estimates to impossibly large problems. And while never exact, his guesses often landed within an order of magnitude of the actual number—enough, in other words, to act upon. Today we’re following Fermi’s lead, applying the power of Big Data to approximate answers to the Big Questions.


pages: 559 words: 155,372

Chaos Monkeys: Obscene Fortune and Random Failure in Silicon Valley by Antonio Garcia Martinez

Airbnb, airport security, always be closing, Amazon Web Services, Burning Man, Celtic Tiger, centralized clearinghouse, cognitive dissonance, collective bargaining, corporate governance, Credit Default Swap, crowdsourcing, death of newspapers, disruptive innovation, drone strike, El Camino Real, Elon Musk, Emanuel Derman, financial independence, global supply chain, Goldman Sachs: Vampire Squid, hive mind, How many piano tuners are there in Chicago?, income inequality, information asymmetry, interest rate swap, intermodal, Jeff Bezos, Kickstarter, Malcom McLean invented shipping containers, Marc Andreessen, Mark Zuckerberg, Maui Hawaii, means of production, Menlo Park, minimum viable product, MITM: man-in-the-middle, move fast and break things, move fast and break things, Network effects, orbital mechanics / astrodynamics, Paul Graham, performance metric, Peter Thiel, Ponzi scheme, pre–internet, Ralph Waldo Emerson, random walk, Ruby on Rails, Sam Altman, Sand Hill Road, Scientific racism, second-price auction, self-driving car, Silicon Valley, Silicon Valley startup, Skype, Snapchat, social graph, social web, Socratic dialogue, source of truth, Steve Jobs, telemarketer, undersea cable, urban renewal, Y Combinator, zero-sum game, éminence grise

Next up was Rohit Dhawan. Another Googler, he had that very well put together and confident air of someone who felt he had mastered his field of work (he was a Penn grad, of course). His angle was analytical ability, and he asked me a variant of that legendary Enrico Fermi brainteaser about piano tuners in Chicago. His variant was to estimate the number of planes in the sky at any given moment. It required nothing more than some rough base assumptions about number of airports and flights per day, and then some dimensional analysis that got us within an order of magnitude of reality, and we were done in ten minutes.


pages: 260 words: 77,007

Are You Smart Enough to Work at Google?: Trick Questions, Zen-Like Riddles, Insanely Difficult Puzzles, and Other Devious Interviewing Techniques You ... Know to Get a Job Anywhere in the New Economy by William Poundstone

affirmative action, Albert Einstein, big-box store, Buckminster Fuller, car-free, cloud computing, creative destruction, en.wikipedia.org, full text search, hiring and firing, How many piano tuners are there in Chicago?, index card, Isaac Newton, Johannes Kepler, John von Neumann, lateral thinking, loss aversion, mental accounting, Monty Hall problem, new economy, Paul Erdős, RAND corporation, random walk, Richard Feynman, rolodex, Rubik’s Cube, Silicon Valley, Silicon Valley startup, sorting algorithm, Steve Ballmer, Steve Jobs, The Spirit Level, Tony Hsieh, why are manhole covers round?, William Shockley: the traitorous eight

He spent much of his lunch calculating how many extraterrestrial civilizations there were in the universe and how close the nearest one would be. This was the classic “Fermi question.” Back at the University of Chicago, Fermi tormented his students with only somewhat easier questions. His most famous classroom riddle was, “How many piano tuners are there in Chicago?” Fermi staunchly believed that anyone with a PhD in physics should be able to estimate just about anything. Somewhere along the line the “PhD in physics” part got dropped. Today’s employers have gotten the idea that everyone, including humanities majors, should be able to estimate odd quantities on a job interview.


pages: 335 words: 95,280

The Greatest Story Ever Told--So Far by Lawrence M. Krauss

Albert Einstein, complexity theory, cosmic microwave background, cosmological constant, dark matter, Ernest Rutherford, How many piano tuners are there in Chicago?, Isaac Newton, Magellanic Cloud, Murray Gell-Mann, RAND corporation, Richard Feynman, Richard Feynman: Challenger O-ring, the scientific method

He refined his abilities and helped his students do so by inventing what we now call Fermi Problems, which he is also said to have assigned at lunchtime each day to the team working for him. My favorite problem, which I always assign to my introductory-physics students, is “How many piano tuners are there in Chicago?” Try it. If you get between one hundred and five hundred, you did well. Fermi won the Nobel Prize for his experimental work, but his theoretical legacy for physics may be far greater. True to form, the “theory” he proposed in his famously rejected paper on neutron decay was remarkably simple, yet it did the job.


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pages: 212 words: 68,754