planetqhe and the IB

Random Behaviour

Experimental vs Theoretical

Compound Events I

Compound Events II

Expectations and Distributions

Distributions and Hypotheses

Probability in the real world



Essential Questions

Smart Luck

Les Abattoirs


uk lottery

stock market predictions

Your stories

Royal Navy



In this section you can contribute and/or read stories that users have submitted about their experiences with the world of probability. Some of them could be useful discussion starters, or might give you food for thought for a TOK essay......Send entries to me here and I will post them.


Luke's (Y13) Backgammon playing Mounty in Canada:

I once met a Mounty in Vancouver who played Backgammon religiously; he recorded all the values of his dice throws in a small brown book. Over fifteen years of playing Backgammon he accumulated a large array of results, he then plotted these on a graph a came up with some startling results……. from his results he formulated a theory that: "luck travels in a wave pattern" he then continued to monitor his results as he played, and he found that as long as the person throwing was relaxed and in the correct frame of mind this was true……he went on to become a better player because he was sure that he could predict whether his (or his opponents) next throw would be high or low.


From the Scotland on Sunday Newspaper back page: The past may find you out: previous performance is not always reliable for predicting what happens in the future Sunday November 5th 2000, regarding regulation on financial products advertisements:

In the mid-1980's, an academic from Exeter University concluded that relying on past investment performance had less chance of predicting future success than betting on greyhounds using the the winning trap numbers of the previous meeting. ....the Financial Services Authority has finally decided to [act]. After its own research this year validated that of the Exeter professor, it has set up a task force to probe the use of past performance figures in ads.

However, a blanket ban is unlikely. Instead, the Past Performance in Advertising will "consider whether the rules need adjusting". Don't hold your breath. The report will take until next summer, and perhaps a further year to implement. In the meantime, it is down to individuals to take care of themselves.


An excerpt from Darrel Huff's excellent book "How to take a chance": Huff tells the story of a run on black in a Monte Carlo casino in 1913: came up a record twenty-six times in succession. Except for the question of the house limit, if a player had made a one-louis ($4) bet when the run started and pyramided for precisely the length of the run on black, he could have taken away 268 million dollars. What actually happened was a near-panicky rush to bet on red, beginning about the time black had come up a phenomenal fifteen times...players doubled and tripled their stakes (believing) that there was not a chance in a million of another repeat. In the end the unusual run enriched the Casino by some millions of francs.


A true story about a van driver from Bristol by David Harris:

The driver who moved my belongings to Bristol from London gave me a really cheap quote. When I asked him how he managed to keep his price so low, he told me that he had cancelled the insurance on his van. He reasoned that since he had made no claim for 25 years, paying for insurance was a waste of money.

To me this seems just as wrong a piece of reasoning as believing that H is more likely than T after throwing three H's. My Professor at The Graduate School of Education disagreed:

...surely the fact that he hadn't had an accident for 25 years suggests that there is something about his driving which relates to not having an accident. Some people do have more accidents than other people. This situation seems different to me to be different from the situation of throwing a coin.



The Representative Fallacy:

The UK National Lottery is a 6/49 system - you have to correctly pick 6 numbers drawn at random without replacement from the numbers 1 through 49. Many lotteries in other countries have very similar systems. You'll be familiar with the types of superstition and 'schemes' people have for winning. The Representative Fallacy is a commonly held misconception about probability that states that one event is more likely than another just because it appears more representative of a typical element of the sample space. Here's a familiar example: What is more likely to win the UK National Lottery; {1,2,3,4,5,6} or {4,11,23,31,37,41}? Our intuition tells us that you'd be crazy to pick the first set of numbers - they seem so unusual - but they are just as likely as the other set.


An excerpt from Darrel Huff's excellent book "How to take a chance": The story of the Pitosfky family:

In more than a century, seven generations of the Pitofsky family have produced only sons. In 1959 the forty-seventh consecutive boy in the line was born to Mr and Mrs Jerome Pitofsky of Scarsdale NY, or so the New York Times reported. Assuming no overlooked girls and no distortions of the record in the interests of a marvel, this is a one-chance-in 136 trillion (A US trillion equals a British billion) occurrence. While pondering its significance, you may want to consider this: the pattern of the last forty-seven births in YOUR family is also one that would occur just once in 136 trillion times...on the average.


What happened when David Harris checked his order list at IST, August 1999:

I was checking off a long list of books and other equipment that I had ordered for school in the D and T workshop, which was at that time completely empty. I couldn't find one item on the list , and my eye made several 'scans' of the list of items with no result. I lost patience and thought "Oh well, I suppose it is not there". An instant later, I found the item - right at the top of the page! Subconsciously, I judged that I was more likely to find the item somewhere in the middle 75% or so of the list. The mistake I made was that the individual item was just as likely to appear in any position - top, bottom or any other place. All this despite my "Firm grasp" of probability..................


The coincidence of Richard's wife:

Richard's wife, Adriana, is Columbian. She has three children, two of whom are twins. She met another Columbian woman here in Toulouse. She also has twins - born on the exact same day that Adriana's were born! (How could you find the probability of Adriana meeting such a woman? What types of events are there in this story? What information would you need to do so? How exact would your answer be?)