statistics

What Are the Odds Two People in the Room Have the Same Birthday?

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Photo: surlygirl

Situations arise from time to time where you are in a room with a whole bunch of strangers. They key to making friends and the opposite sex swoon? Probability.

What are the odds that two people in the room have the same birthday? Memorize some of these numbers so that you can spout them off, I guarantee you will be the coolest guy in the room – 9 people = 10%, 13 = 20%, 15 = 25%, 18 = 35%, 23 = 51%, 57 = 99%, 366 = 100%.

It’s important that you mention the assumptions before your new worshipers start poking holes in you numbers – random distribution of birthdays, no leap years, no twins, etc. Then you can go into what is interesting – with only 23 people in the room, odds are two people share a birthday. It only takes 57 people to jump to 99% probability, but to get to 100% you need to have 366 people.

Now to really make their mouths drop. How many people would it take for the odds to be in your favor for someone having the same birthday as you? 253. They may question you because this is much higher than 365/2, but stick to your guns and point out that two of the other people could have the same birthday. How many people would it take for two to likely have a birthday within a week of each other? Only 7. Ya, but a random distribution is a hell of an assumption. Oh really? Actually the odds are slightly more in your favor because birthdays tend to clump – summer babies, C-sections aren’t on weekends, and so on.

Here’s one to set up on a tee for them: what are the odds that two people have the same half birthday? If they can figure this out, you may just have found your soulmate.

The Benefits of Being the Youngest Child

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Photo: Joel Dinda

I recently came across a study that examined how two brothers who are both professional baseball players approach the game differently. The Berkeley researchers actually had a pretty good sample size to work with – over 700 brothers have played in the majors. Their hypothesis was that the younger siblings take more risk.

Stolen base attempts are the most obvious element of the game to inspect. The result? Younger brothers are 10.6 more times likely to steal. They also noticed the younger brother is more likely to be hit by a pitch which means they probably crowd the plate slightly more. The research paper even extends beyond baseball as well – younger siblings are more likely to engage in dangerous sports across the board like football and skydiving.

This study is not proposing any new theories – older siblings are generally more conservative and younger ones take more risks. So why is it cool? Well first, I appreciate that it relates this idea to baseball. More importantly, other studies have shown that risk takers are happier overall. Thus, through the transitive property of equality, younger siblings are happier. QED.

A Few Facts About the Netherlands to Share at Your Next Cocktail Party

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The Netherlands is always listed as one of the happiest, most democratic, most liberal, and tourist friendly nations. Boring! Here are a couple interesting facts you probably don’t know:

  • Orange is not their official color even though that is all they wear at the World Cup and Olympics. The official colors? Red, white, and blue! So why do they wear orange? To honor the royal family, the House of Orange-Nassau.
  • Marajuana is actually illegal in Amsterdam (and all of the Netherlands), but the law is deliberately not enforced. – by leaving the law on the books they are in compliance with international drug agreements. What is the “unofficial” policy of their judicial system? A person can possess up to 5 grams and a “coffee shop” can have up to 500 grams as long as it doesn’t distribute more than 5 grams per person daily. Because it is technically illegal the government only receives income tax on the proceeds, rather than jacking up the tax rate like we do for cigarettes.
  • The Netherlands is possibly the country with the most to lose from global warming – a whopping 50% of its land is less than 1 meter above sea level. In only 200 years the portion of the Netherlands below sea level is expected to go from a fifth to a well over half. Maybe that is why the are kicking the worlds butt at making use of renewable energy?

Answering the Question: Is Driving to the Airport More Dangerous than Flying?

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Photo: Luis Argerich

A person with an irrational fear of flying is frequently told “you’re more likely to die driving to the airport than on the flight” – is this actually true or just calming words?

Let’s look at some statistics
From the perspective of a passenger in the car/airplane:

  • Driving = 1 fatality per 88 million miles driven (excluding motorcycles which have a 25 times higher death rate and any pedestrians/bikers killed by cars)
  • Scheduled flights (mainly airlines) = 1 fatality per 64 million miles flown

(These numbers would skew in favor of airplanes if you cared about how many people were transported. But, knowing my readers as well as I do, you only care about yourself.)

It looks like the expected value of death favors driving, but I would argue that you should be trying to avoid fatal accidents all together – if you are in one, it is a crap shoot whether or not you are the one that dies. This is definitely not a situation I want to be in, otherwise I would play Russian Roulette.

  • Driving = 1 fatal accident every 76 million miles driven
  • Scheduled flights = 1 fatal accident every 2 billion miles flown

What are the odds of surviving this so called Russian Roulette?
Each fatal plane crash averages over 30 deaths, which is only 42% of the passengers on the flights. On the other hand each fatal driving accident averages 1.15 driver/passenger deaths. Unfortunately it is harder to track the number of occupants or even cars involved in these collisions. My approximation is 3 people involved – most cars have only the driver aboard, and the ones that do not are offset by solo car crashes. If the number is 2.75, this would equal the 42% survival rate for being in a fatal plan crash. Pretty darn close!

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The Ethics of Using Information Attained by Unethical Means

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Photo: Jason Scragz

I love attaining knowledge, but here is a puzzling question – is it ethical to use information gained in an unethical way? If so, are we just supposed to turn a blind eye to how it was obtained and move on? If not, are we just supposed to forget the knowledge we gained and pretend it never happened? Neither option jumps out as the right answer, so let’s inspect a couple examples.

Using the Information
How about an extreme example – let’s take a look at the Nazis, some of the least ethical people ever. They did a whole series of messed up experiments on human prisoners that resulted in thousands of deaths and countless more ended with dismemberment, disability, or at the very least emotional torment. Just to give you an idea, some of the tests were carried out to find out the the effects on the human body of extreme cold and heat, mustard gas and other poisons, altitude, and drinking salt water.

Today we know a lot about the limits of the human body because the Nazis forced thousands of people past the limit and did not stop until they were dead. For example, we now know that you die from hypothermia when your body temperature reaches approximately 77 degrees Fahrenheit. Researchers today openly use the Nazi experiment data and are determined to see good come from all the deaths by using it to help others in the future. Here is a good essay examining the ethical debate of using this data.

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Personal Informatics – What Gets Measured Gets Managed

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Photo: Tyrone Shum

The often quoted Peter Drucker said “what gets measured gets managed.” If you can’t measure it you are merely guessing, not managing. Of course he was referring to applying metrics to better manage a business, but the same principle applies to individuals as well. How are you to optimize your life when you do not measure how exactly you spend it?

Personal Finance
Personal finance is the best example of this — in order to get your spending under control and save money you first need to know where your money is being spent. Track where your money is going, create a budget to control problem areas, and continue tracking to observe the improvements. Mint.com is a terrific website to help individuals focus on tracking their expenses. From their website:

If you’ve tried to build a budget in the past and just couldn’t stick to it, we understand. Until now, trying to see where you’re spending and where you can cut back has been too difficult. But once you understand a few basic principles and start tracking your spending with Mint.com, you’ll be able to set and stick to realistic goals, easily and automatically.

Mint.com has developed impressive technology to easily track and report on your spending – in turn allowing more people to stick to their financial goals. This website is only one example in an abundance of new tools utilizing technology to help you track your life. Beyond personal finance, there are similar services you can use to for almost any facet of your life.

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Eye Opening Abortion Statistics

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Photo: Matt Smith

Abortion is a hot button issue in the United States and nearly everyone has an unwavering opinion – there is no argument that can be made here that will instantly change your belief. Instead I will share with you some eye opening statistics regarding abortion and let you draw your own conclusions.

I am not one to wholeheartedly believe in statistics as a statistic can be dug up (or created) to support any viewpoint. My main issue with taking statistics at face value is that there can be numerous errors in the study which are reflected in the final data. Is it truly a random sample? Is it a big enough sample to draw any conclusions? Was the study funded by an organization that had an interest in the results coming out a certain way? Fortunately, abortion is not a difficult activity to track as nearly all abortions take place in a hospital or abortion clinic. The healthcare industry accurately tracks everything – in a 2008 sample of 100 hospitals there were 4 injuries relating to slicing zucchini, including one for trying to slice it with a mandolin …

In the case of abortion the margin of error is largely irrelevant — are you even able to come up with a ballpark answer? How common are abortions? 5% of all pregnancies? 10%? 20%? 40%? Higher?

In the United States 20% of all pregnancies result in an abortion. What’s interesting is that this number varies greatly across the country and the world. The District of Columbia and New York are close to 40% while many rural states are under 10%.

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