Download - How to Estimate Anything
HOW TO ESTIMATE ANYTHINGLearning Night - 01/21/15
WHAT I’M TALKING ABOUT TODAY• What is a Fermi Estimation?
• An example to get us going…
• Some tips and tricks
• Try it yourself!
• Skeptical?
EVER WONDER HOW MANY OR HOW OFTEN SOMETHING HAPPENS?
HOW MANY PIANO TUNERS ARE IN SAN FRANCISCO?
PIANO TUNERS IN SF• 1M people in SF
• 2 people per household
• 1/20 households have a piano
• each piano tuned once a year
• 2 hours to tune a piano
• tuners work full time for 40 hours a week
THE MATH
• 1M people / 2 people per household = 500K households
• 500K * 1 / 20 pianos/household = 25 000 pianos = 25 000 piano tunings per year
• 1 hour to tune a piano = 100 000 piano tuning hours
• 100 000 hours / 2 000 hours per piano tuner = ~50 piano tuners!
USEFUL FOR…
• Interviews!
• Satisfying personal curiosity
• Trying to figure out whether or not Maroon 5 really crashed all those weddings…
TACTICS
• Top down vs. Bottoms up
• Give a range!
• Easy numbers = Good numbers
• Key is make assumptions based on what you know
HOW MANY PEOPLE ARE NAMED JONATHAN IN THE WORLD?
LOL. WHAT A DOUCHE.
• Jonathan is a Male name
• 50% of population is Male
• Only Westernized civilizations will name kids Jonathan (2B people)
• 1/16 Males named some variation of Jonathan (Jon, John, Johnathan etc)
• 3B * 50% * 1/16 = 62.5M people named Jonathan
SKEPTICAL?
• Fermi is for…
• quick estimates
• magnitude
• starting points
"FERMI ESTIMATES WORK BECAUSE THE ESTIMATIONS OF THE INDIVIDUAL TERMS ARE OFTEN CLOSE TO
CORRECT, AND OVERESTIMATES AND UNDERESTIMATES HELP CANCEL EACH OTHER OUT. "