Lars P. Syll

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Science and crossword solving The model is not . . . how one determines the soundness or otherwise of a mathematical proof; it is, rather, how one determines the reasonableness or otherwise of entries in a crossword puzzle. . . . The crossword model permits pervasive mutual support, rather than, like the model of a mathematical proof, encouraging an essentially one-directional conception. . . . How reasonable one’s confidence is that a certain entry in a...

Econometrics — the danger of calling your pet cat a dog The assumption of additivity and linearity means that the outcome variable is, in reality, linearly related to any predictors … and that if you have several predictors then their combined effect is best described by adding their effects together … This assumption is the most important because if it is not true then even if all other assumptions are met, your model is invalid because you have described...

In the year 2525 .[embedded content]

But once … we were here .[embedded content] One of the greatest movie scenes ever. In loving memory of my brother, Peter ‘Uncas’ Pålsson.

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I The Book of Why för Judea Pearl fram flera tunga skäl till varför den numera så populära kausala grafteoretiska ansatsen är att föredra framför mer traditionella regressionsbaserade förklaringsmodeller. Ett av skälen är att kausala grafer är icke-parametriska och därför inte behöver anta exempelvis additivitet och/eller frånvaro av interaktionseffekter — pilar och noder ersätter regressionsanalysens nödvändiga specificeringar av funktionella relationer mellan de i...

Ignorability and other questionable assumptions in causal inference Most attempts at causal inference in observational studies are based on assumptions that treatment assignment is ignorable. Such assumptions are usually made casually, largely because they justify the use of available statistical methods and not because they are truly believed. Marshall Joffe et al. An interesting (but from a technical point of view rather demanding) article on a highly...

Applied econometrics — a messy business The applied econometrician is like a farmer who notices that the yield is somewhat higher under the trees where birds roost, and he uses this for evidence that bird droppings increase the yield. However, when he presents his findings … another farmer … objects that he used the same data but came up with the conclusion that moderate amounts of shade increase the yields … A bright chap … then observes that these two...

Celebrating our twentieth anniversary, yours truly and wife spend a couple of days at our favorite hotel — Koldingfjord — in Denmark.