European Association
of American Square Dancing Clubs e.V.

Friendship is Square Dancing's greatest reward


EAASDC-Bulletin May 2011

Editor's Page


No, the report in the last Bulletin about Angela Merkel wasn’t an April fools' joke. It’s true. Here another proof.

Ok, I admit: That's hokey! Angela Merkel didn’t learn Square Dancing, sad but true. Perhaps somebody can convince her some time.

However some reactions on the April fool’s joke also were saddish. Our president told me that there were several phone calls of Bulletin readers complaining about the article. They claimed to be offended and outraged, they were threatening to cancel their subscription and complained about the incompetence of the Board. And that it was misuse of the Bulletin to publish such an article. Apparently they tried to call the given phone number and after they noticed that nobody was answering, they phoned official authorities of the German government. And they then were furious about the result, when they noticed the story was not true. At least that’s what I was told.

Ok, put all the blame on me! I will try to avoid any humoristic items in the future. So I hereby apologize. But I am a bit scared and amazed about the reaction of Square Dancers. And I had expected that Square Dancers are faster in realizing facts and slightly more tolerant. And it has not been the first April fools' joke in a March Bulletin ever, my predecessors also published such things.

Another disclaimer has to be made. Our reader Ralf Bender is mathematician and he made a comment on the article Dance Education on page 79ff of the March Bulletin.

Ralf Bender says:


The author tried to calculate the joint probability of a square to dance a sequence correctly from the probabilities of the individual dancers. The probability of a square composed of eight dancers each with a 90% probability of dancing error-free is given as .9 x .9 x .9 x .9 x .9 x .9 x .9 x.9 = .4305 = 43%

However, this formula to calculate joint probabilities from individual probabilities is only correct if the individual events are independent. The formula is applicable for eight dancers in different squares (if possible in different halls), but not for eight dancers in the same square, in which the dancers (let us hope) are not dancing independently from each other.

How can we calculate the joint probability of the square from the individual probabilities? Not at all. There are assumptions required for the pattern of dependencies in the square. However, there are so many factors influencing the dependencies in a square (properties of the dancers, caller, mood in the hall, ...) that it is difficult to formulate an appropriate (statistical) model. Although theoretically possible, such a model would be very complicated and nevertheless only an insufficient description of the truth. The dependencies in a square (and other things of life) are quite complex and variable and cannot be adequately quantified by simple numbers. So I won't even try that.

The dependencies within a square were taken into account in the article. However, the method used was grossly false (from the sight of probability calculation). On page 84 and following, the dancers who can correct the errors of other dancers get a "probability" of more than 100%. This is nonsense or at least has nothing to do with probability calculation. A probability always lies between 0 and 100% (limits included), or it is no probability. (For experts: This follows from the axioms of Kolmogorow.) All the following calculations and numbers are
based on this false concept and have no meaning at all.

I underline that my critique only addresses the meaningless probability calculations and not the main statements of the article. My tip: If someone has good arguments for any point of view, then one should present these arguments. An assistance of the arguments by means of statistics is often unnecessary (and bores most of the readers). However, if statistics and probability should be used then consult someone who understands the basic rules of probability calculation. There is the risk that good arguments are weakened by the use of false and meaningless numbers.

Thank you Ralf!

I shouldn’t forget to mention that the special student’s issue of the Bulletin will be distributed a few days after this Bulletin. Some more copies than ordered will be printed; so if you forgot to place your order: contact Silke Wilhelm soonest. May be she can fulfill your additional request.

I would like to close with a nice saying, given to me by Heiner Fischle:

My secret wish is that people may not merely have fun with square dance, but have joy dancing. But perhaps that’s too much to ask for?

With this Heiner comments the letters about “joy” in Square Dancing in the February Bulletin on page 69 and the March Bulletin on page 73.

Nothing more to say.

Klaus Rohrbach editor(at)eaasdc.eu

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