Pascals Triangle, Home Work and Root Cause Analysis

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  • Excellent article.

    Even better, I see you used to work in Manchester!



  • I enjoyed your article because it was relevant on multiple levels. Thank you for a well-written article!

  • Hi David,

    This is fantastic! I can find many uses for this..


    John R

  • Good article.

    Of course, the point you omitted is how the actual probability of any given failure alters the calculations.

    With the lottery example, because each of the numbers is (supposedly) equally likely to be chosen, Pascal's triangle is a perfect model, and shows the true (im)probability of winning.

    With the car example, QA testing ensures that parts generally have a much higher probability of working than failing, thus although there's only one way for the whole system to work perfectly, it's more likely than the millions of ways it can fail.

  • Yes, and apparently each space shuttle launch expected at least 6000 components to fail but was still designed to work.

    On my list of things not to think about is precisely how fast a piece of metal moves inside a motor-bike engine when it's between your legs:-P

  • Joe, I should have remembered that. I think one of your books mentioned storing a calendar table rather than trying to workout calendar maths on the fly.

    It is so easy to forget that storing a few thousand records for utility sets costs next to nothing but delivers one hell of a lot of utility

  • Thanks for the great article. It reminds me of why when I used to fly airplanes my instructor kept telling me that the probability of an engine failure in a twin engine plane was twice as high as a single... of course you still had one engine running in a twin.

    do it right, or do it over and over, it's up to you

  • Don't you also need to make sure that @n <> @r so you don't divide by 0? And @r <> 0 either.

  • CELKO - your code does not compile. Looks like some logic is missing in the case statement.

    I don't get " SELECT fact FROM Factrorials WHERE @f = @n " I @f supposed to be a column or a variable?

    I like the idea of it and the recommendation of storing calendar data in table.

  • Nice article.

    Jason...AKA CirqueDeSQLeil
    I have given a name to my pain...MCM SQL Server, MVP
    Posting Performance Based Questions - Gail Shaw[/url]
    Learn Extended Events

  • As a teenager I had a job delivering potatoes to fish and chip shops across the staffordshire plains. The boss had a book called a ready-reckoner to help calculate the bills.

    I remember the books of sin/cos/tan tables, normal distribution figures etc. I also remember that they would contain small rounding errors on specific values as a means of checking whether or not a rival publisher had violated the copyright.

    My first IT job had me loading 1/4 inch tapes for backup purposes. You had to master a strange TiChi maneuver to get the ultimate efficient loading technique!

    Then there was the short straw of having to crawl through the roof space with a crimping tool to wire up a 25 pin plug to connect the mini-computer to dumb terminals. A job made harder by the fact that the boss used to bribe us with whiskey!

    Happier times, and as Phil Factor once described, a time when having an interesting personality disorder was a pre-requisite for a career in IT.

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