I mean just think about going to class and learning the odds of dying in your burning pajamas! The kids would go crazy!

Odd are probabilities put in another form. For instance, toss a coin and the odds are 1:1 that you’ll get heads (or tails). The probability of getting heads (or tails) is P(H) = 1/2.

Notice that when you add the numbers in the odds form, 1:1, you get 2, which happens to be the denominator of the probability fraction.

So you can always turn odds into a probability by adding the numbers in the odds, putting that in the denominator for the probability form. In the numerator, you put the other odds number.

So the odds of dying in your pajamas is 1:97,000,000.

The probability of dying in your pajamas is P(PJ) = 1/97,000,001

You can compute probabilities from the basic ratio formula. Let E be some event. Then, the probability of E occuring is

P(E) = # ways E can occur / total # outcomes.

With this formula, you just have to count the differents ways things can happen.

For instance, roll a die. The total possible outcomes are {1,2,3,4,5,6}.

What is the probability of rolling an even number?

Well, there are three ways to roll an even number, 2, 4, 6 out of the six total possible outcomes. So the probability of rolling an even number is

P(even) = 3/6 = 1/2 or 50%.

What’s the probability that you’re going to ride your bike on the bike path today? Look at the past 100 days. Out of those days, how many days did you ride your bike? Suppose you rode your bike 85 out of the past 100 days. Then you could say that there was an 85/100 or 85% chance that you’re going to ride your bike today.

With this method, the more days you have measured, the better the probability. LIke, it would be better to make a ratio of the past 1000 days for a more accurate picture. Or, you could get even more detailed and only count days that have the same weather conditions as today and see how many days you rode your bike on days with the same weather conditions, etc…

anyway, that ratio is a pretty good way to use probability in a simple, but revealing way.

And sleep naked!!

]]>Thanks for the post. I understand it but not well enough to use it. My math brain was destroyed in grade 11 by a really obnoxious teacher. I’d love to revive it, but it would probably take a lot more patience than you have to spare. Anyway, if you have any simple examples of how I might be able to formulate probabilities in day to day living I’d love to hear them.

Here’s a collection of probabilities I came across and saved recently.

Odds of being struck by lightning (though not necessarily dying) in a given year: 1 in 400,000 (Source: National Weather Service)

Odds of dying in a car accident in a given year: 1 in 18,400 (Source: National Safety Council [NSC])

Odds of getting killed somehow while walking around outside: 1 in 49,000 (NSC)

Odds of drowning: 1 in 88,000 (NSC)

Odds of choking to death: 1 in 97,000 (NSC)

Odds of dying in an air (or space) accident: 1 in 392,000 (NSC)

Odds of freezing to death: 1 in 469,000 (NSC)

Odds of death from falling off the bed or a chair: 1 in 347,000 (NSC)

Odds of choking to death on your own vomit: 1 in 740,000 (NSC)

Odds of getting killed by fireworks: 1 in 26,440,000 (NSC)

Odds of death due to overly hot tap water: 1 in 11,100,000 (NSC)

Odds of death due to burning pajamas: 1 in 97,000,000 (NSC, and no that’s not a joke)

Odds that you’ll kill yourself: 1 in 9,200 (NSC)

JH