Hidden Markov Models and Bayes Theorem for dummies

22 Jan, 2019 at 15:57 | Posted in Statistics & Econometrics | Comments Off on Hidden Markov Models and Bayes Theorem for dummies

 

Beyond probabilism

20 Jan, 2019 at 17:22 | Posted in Statistics & Econometrics | Comments Off on Beyond probabilism

“Getting philosophical” is not about articulating rarified concepts divorced from statistical practice. It is to provide tools to avoid obfuscating the terms and issues being bandied about …

mayoDo I hear a protest? “There is nothing philosophical about our criticism of statistical significance tests (someone might say). The problem is that a small P-value is invariably, and erroneously, interpreted as giving a small probability to the null hypothesis.” Really? P-values are not intended to be used this way; presupposing they ought to be so interpreted grows out of a specific conception of the role of probability in statistical inference. That conception is philosophical. Methods characterized through the lens of over-simple epistemological orthodoxies are methods misapplied and mischaracterized. This may lead one to lie, however unwittingly, about the nature and goals of statistical inference, when what we want is to tell what’s true about them …

One does not have evidence for a claim if nothing has been done to rule out ways the claim may be false. If data x agree with a claim C but the method used is practically guaranteed to find such agreement, and had little or no capability of finding flaws with C even if they exist, then we have bad evidence, no test …

Statistical inference uses data to reach claims about aspects of processes and mechanisms producing them, accompanied by an assessment of the properties of the inference methods: their capabilities to control and alert us to erroneous interpretations. We need to report if the method has satisfied the most minimal requirement for solving such a problem. Has anything been tested with a modicum of severity, or not? The severe tester also requires reporting of what has been poorly probed … Informal​ statistical testing, the crude dichotomy of “pass/fail” or “significant or not” will scarcely do. We must determine the magnitudes (and directions) of any statistical discrepancies warranted, and the limits to any substantive claims you may be entitled to infer from the statistical ones.

Deborah Mayo’s book underlines more than anything else the importance of not equating science with statistical calculation or applied probability theory.

The ‘frequentist’ long-run perspective in itself says nothing about how ‘severely’ tested are hypotheses and claims. It doesn’t give​ us the evidence we seek.

And ‘Bayesian’ consistency and coherence are as silent. All science entail human judgement, and using statistical models doesn’t relieve us of that necessity. Choosing between theories and hypotheses can never be a question of inner coherence and consistency.

Probabilism — in whatever form it takes — says absolutely​ nothing about reality.​

Finland’s Universal Basic Income experiment — an evaluation

20 Jan, 2019 at 16:29 | Posted in Economics, Politics & Society | Comments Off on Finland’s Universal Basic Income experiment — an evaluation

 

Results on the first year of the Finnish UBI experiment will become available in a couple of months, and a final report — covering the whole two-year time-span — is scheduled for publication in 2020.

Freiheit ist immer Freiheit der Andersdenkenden

20 Jan, 2019 at 12:47 | Posted in Politics & Society | 1 Comment


Rosa Luxemburg (1871-1919)

Och de döda skall icke tiga men tala

20 Jan, 2019 at 11:55 | Posted in Politics & Society | 1 Comment

Till Fadime Sahindal, född 2 april 1975 i Turkiet, mördad 21 januari 2002 i Sverige

fadimeI Sverige har vi länge okritiskt omhuldat en ospecificerad och odefinierad mångkulturalism. Om vi med mångkulturalism menar att det i vårt samhälle finns flera olika kulturer, ställer detta inte till med problem. Då är vi alla mångkulturalister. Men om vi med mångkulturalism menar att det med kulturell tillhörighet och identitet också kommer specifika moraliska, etiska och politiska rättigheter och skyldigheter, talar vi om något helt annat. Då talar vi om normativ multikulturalism. Och att acceptera normativ mångkulturalism, innebär också att tolerera oacceptabel intolerans, eftersom den normativa mångkulturalismen innebär att specifika ‘kulturella’ gruppers rättigheter kan komma att ges högre dignitet än samhällsmedborgarens allmänmänskliga rättigheter – och därigenom indirekt bli till försvar för dessa gruppers (eventuella) intolerans. I ett normativt mångkulturalistiskt samhälle kan institutioner och regelverk användas för att inskränka människors frihet utifrån oacceptabla och intoleranta kulturella värderingar.

Den normativa mångkulturalismen innebär att individer på ett oacceptabelt sätt reduceras till att vara passiva medlemmar av kultur- eller identitetsbärande grupper. Men tolerans innebär inte att vi måste ha en värderelativistisk inställning till identitet och kultur. De som i vårt samhälle i handling visar att de inte respekterar andra människors rättigheter, kan inte räkna med att vi ska vara toleranta mot dem.

Om vi ska värna om det moderna demokratiska samhällets landvinningar kan samhället inte omhulda en normativ mångkulturalism. I ett modernt demokratiskt samhälle måste rule of law gälla – och gälla alla!

Mot dem som i vårt samhälle vill tvinga andra att leva efter deras egna religiösa, kulturella eller ideologiska trosföreställningar och tabun, ska samhället vara intolerant. Mot dem som vill tvinga samhället att anpassa lagar och regler till den egna religionens, kulturens eller gruppens tolkningar, ska samhället vara intolerant.


DE DÖDA

De döda skall icke tiga men tala.
Förskingrad plåga skall finna sin röst,
och när cellernas råttor och mördarnas kolvar
förvandlats till aska och urgammalt stoft
skall kometens parabel och stjärnornas vågspel
ännu vittna om dessa som föll mot sin mur:
tvagna i eld men inte förbrunna till glöd,
förtrampade slagna men utan ett sår på sin kropp,
och ögon som stirrat i fasa skall öppnas i frid,
och de döda skall icke tiga men tala.

Om de döda skall inte tigas men talas.
Fast stympade strypta i maktens cell,
glasartade beledda i cyniska väntrum
där döden har klistrat sin freds propaganda,
skall de vila länge i samvetets montrar.
balsamerade av sanning och tvagna i eld,
och de som redan har stupat skall icke brytas,
och den som tiggde nåd i ett ögonblicks glömska
skall resa sig och vittna om det som inte brytes,
för de döda skall inte tiga men tala.

Nej, de döda skall icke tiga men tala.
De som kände triumf på sin nacke skall höja sitt huvud,
och de som kvävdes av rök skall se klart,
de som pinades galna skall flöda som källor,
de som föll för sin motsats skall själva fälla,
de som dräptes med bly skall dräpa med eld,
de som vräktes av vågor skall själva bli storm.
Och de döda skall icke tiga men tala.

                                           Erik Lindegren

Svensk skollag — ett skämt

20 Jan, 2019 at 11:09 | Posted in Education & School | Comments Off on Svensk skollag — ett skämt

När Carina lyfte ut en störande elev ur klassrummet anmäldes hon av föräldrarna. Både Skolinspektionen och polisen kom fram till att hon handlat korrekt. Ändå krävdes hennes arbetsgivare på böter för kränkning av eleven. Och själv kände hon sig pressad att sluta sin anställning.

berglin-snoLärare har rätt att rent fysiskt tillrättavisa störande elever. Men de som gör det, och blir anmälda, riskerar sitt jobb …

I september 2018, nästan ett år efter själva händelsen, lade också Skolinspektionen ner sin utredning … Carina var friad. Barn- och elevombudets beslut hanlade inte i första hand om Carinas agerande, utan kritiserade skolan och huvudmannen för att inte ha tagit sitt ansvar och förhindrat att eleven blev kränkt. Men det var hon som hade fått ta smällen och fått sluta sitt jobb.

— Det känns rättsosäkert och fullständigt regelvidrigt. Hur många lärare blir utsatta för detta? undrar hon.

Emma Leijnse/SDS

Och så undrar politiker varför det är så svårt att få tillräckligt många att vilja jobba som lärare i vårt land …

Knut Wicksell — le origini della Teoria Monetaria Moderna

19 Jan, 2019 at 17:52 | Posted in Economics | 2 Comments

Molti economisti mainstream sembrano pensare che l’idea alla base della Teoria Monetaria Moderna sia nuova e nasca da strane idee economiche.

Nuova? Strane idee? Che ne diciamo di leggere uno dei grandi fondatori dell’economia neoclassica – Knut Wicksell. Questo è ciò che Wicksell scrisse nel 1898 sui “sistemi di puro credito” in Interesse Monetario e Prezzi dei Beni (Geldzins und Güterpreise), 1936 (1898), p. 68f:

wicksell_-_geldzins_und_güterpreise,_1936_-_5770488E’ possibile andare oltre. Non c’è affatto alcun bisogno reale di moneta se un pagamento tra due individui può essere compiuto semplicemente trasferendo la somma appropriata di denaro nei registri bancari …

Un sistema di puro credito non è ancora … stato completamente sviluppato in questa forma. Ma qua e là si può trovare nella veste, alquanto diversa, del sistema delle banconote…

Intendiamo perciò, come fondamento per la discussione che segue, immaginare una situazione in cui il denaro in realtà non circola affatto, né in forma di moneta. … né in forma di banconote, ma dove tutti i pagamenti domestici vengono effettuati per mezzo del sistema di giro [bancario – vaglia bancario ndt] e di trasferimenti contabili. Un’analisi approfondita di questo caso puramente immaginario mi sembra utile, perché fornisce una precisa antitesi alla situazione, anch’essa immaginaria di un sistema di contante puro, in cui il credito non svolge alcun ruolo a prescindere [l’esatto equivalente del modello neoclassico frequentemente assunto di “pagamento anticipato” – LPS] …

Per ragioni semplificative, dobbiamo quindi assumere che l’intero sistema monetario di un paese è nelle mani di un unico istituto di credito, dotato di un adeguato numero di sportelli, in cui ogni individuo economico indipendente detiene un conto col quale può firmare assegni.

Quello che la Teoria Monetaria Moderna (MMT) sostiene è esattamente quello che Wicksell provava ad ipotizzare oltre un secolo fa. La differenza è che oggi l’“economia di puro credito” è una realtà e non solo una curiosità teoretica – la MMT descrive un sistema di moneta legale che [al giorno d’oggi] è in funzione in quasi tutti i paesi del mondo.

In tempi moderni le valute legali sono completamente basate su monete fiat. Le valute non hanno più valore intrinseco (come oro e argento). Ciò che dà loro valore è sostanzialmente il semplice fatto che, tramite esse, si devono pagare le tasse. Ciò consente ai governi di esercitare una sorta di “monopolio del business” della valuta, della quale essi non possono mai rimanere senza. A maggior ragione, la spesa diventa l’azione primaria e la tassazione e l’indebitamento sono degradati ad atti secondari. Se abbiamo una depressione, la soluzione, quindi, non è l’austerità. E’ la spesa. I Deficit di bilancio non sono il problema principale, dal momento che la moneta fiat significa che i governi possono sempre emetterne a sufficienza.

Lars P Syll

Funeral Blues

18 Jan, 2019 at 21:43 | Posted in Varia | 1 Comment

Stop all the clocks, cut off the telephone.
Prevent the dog from barking with a juicy bone,
Silence the pianos and with muffled drum
Bring out the coffin, let the mourners come.

Let aeroplanes circle moaning overhead
Scribbling in the sky the message He is Dead,
Put crêpe bows round the white necks of the public doves,
Let the traffic policemen wear black cotton gloves.

He was my North, my South, my East and West,
My working week and my Sunday rest
My noon, my midnight, my talk, my song;
I thought that love would last forever, I was wrong.

The stars are not wanted now; put out every one,
Pack up the moon and dismantle the sun.
Pour away the ocean and sweep up the wood;
For nothing now can ever come to any good.

W. H. Auden

Bengt Nilsson In Memoriam. A friend non plus ultra.

Eres Tú​

18 Jan, 2019 at 21:16 | Posted in Varia | Comments Off on Eres Tú​

 

Eres tú
Como el agua de mi fuente
Eres tú
El fuego de mi hogar
(Eres tú)
Algo así eres tú
(Como el fuego de mi hoguera)
Algo así como el fuego de mi hoguera
(Eres tú)
Algo así eres tú
(El trigo de mi pan)
Mi vida algo así eres tú

A hundred years ago

18 Jan, 2019 at 19:19 | Posted in Politics & Society | 3 Comments

The treaty includes no provisions for the economic rehabilitation of Europe — nothing to make the defeated Central Empires into good neighbours, nothing to stabilize the new states of Europe …

41pkcwxw8il._sx314_bo1,204,203,200_The Council of Four paid no attention to these issues … Reparation was their main excursion into the economic field, and they settled it as a problem of theology, of politics, of electoral chicane, from every point of view except that of the economic future of the states whose destiny they were handling …

The danger confronting us, therefore, is the rapid depression of the standard of life of the European populations to a point which will mean actual starvation for some … And these in their distress may overturn the remnants of organization, and submerge civilization itself in their attempts to satisfy desperately the overwhelming needs of the individual …

In a very short time, therefore, Germany will not be in a position to give bread and work to her numerous millions of inhabitants, who are prevented from earning their livelihood by navigation and trade … “We do not know, and indeed we doubt,” the Report concludes, “whether the delegates of the Allied and Associated Powers realize the inevitable consequences which will take place … Those who sign this treaty will sign the death sentence of many millions of German men, women, and children.”

Paul Krugman — a methodological critique

16 Jan, 2019 at 16:03 | Posted in Economics | 50 Comments

Alex Rosenberg — chair of the philosophy department at Duke University and renowned economic methodologist — has an interesting article on What’s Wrong with Paul Krugman’s Philosophy of Economics in 3:AM Magazine. Writes Rosenberg:

theoryKrugman writes: “So how do you do useful economics? In general, what we really do is combine maximization-and-equilibrium as a first cut with a variety of ad hoc modifications reflecting what seem to be empirical regularities about how both individual behavior and markets depart from this idealized case.”

But if you ask the New Classical economists, they’ll say, this is exactly what we do—combine maximizing-and-equilibrium with empirical regularities …

One thing that’s missing from Krugman’s treatment of economics is the explicit recognition of what Keynes and before him Frank Knight, emphasized: the persistent presence of enormous uncertainty in the economy … Why is uncertainty so important? Because the more of it there is in the economy the less scope for successful maximizing and the more unstable are the equilibria the economy exhibits, if it exhibits any at all …

Along with uncertainty, the economy exhibits pervasive reflexivity: expectations about the economic future tend to actually shift that future … When combined, uncertainty and reflexivity together greatly limit the power of maximizing and equilibrium to do predictively useful economics. Reflexive relations between future expectations and outcomes are constantly breaking down at times and in ways about which there is complete uncertainty.

I think Rosenberg is on to something important here regarding Krugman’s neglect of methodological reflection.

When Krugman responded to my critique of IS-LM this hardly came as a surprise.  As Rosenberg notes, Krugman works with a very simple modelling dichotomy — either models are complex or they are simple. For years now, self-proclaimed “proud neoclassicist” Paul Krugman has in endless harping on the same old IS-LM string told us about the splendour of the Hicksian invention — so, of course, to Krugman simpler models are always preferred.

In a post on his blog, Krugman has argued that ‘Keynesian’ macroeconomics more than anything else “made economics the model-oriented field it has become.” In Krugman’s eyes, Keynes was a “pretty klutzy modeler,” and it was only thanks to Samuelson’s famous 45-degree diagram and Hicks’s IS-LM that things got into place. Although admitting that economists have a tendency to use ”excessive math” and “equate hard math with quality” he still vehemently defends — and always have — the mathematization of economics:

I’ve seen quite a lot of what economics without math and models looks like — and it’s not good.

Sure, ‘New Keynesian’ economists like Krugman — and their forerunners, ‘Keynesian’ economists like Paul Samuelson and (young) John Hicks — certainly have contributed to making economics more mathematical and “model-oriented.”

wrong-tool-by-jerome-awBut if these math-is-the-message-modellers aren’t able to show that the mechanisms or causes that they isolate and handle in their mathematically formalized macromodels are stable in the sense that they do not change when we “export” them to our “target systems,” these mathematical models do only hold under ceteris paribus conditions and are consequently of limited value to our understandings, explanations or predictions of real economic systems.

When it comes to modelling philosophy, Paul Krugman has earlier defended his position in the following words (my italics):

I don’t mean that setting up and working out microfounded models is a waste of time. On the contrary, trying to embed your ideas in a microfounded model can be a very useful exercise — not because the microfounded model is right, or even better than an ad hoc model, but because it forces you to think harder about your assumptions, and sometimes leads to clearer thinking. In fact, I’ve had that experience several times.

The argument is hardly convincing. If people put that enormous amount of time and energy that they do into constructing macroeconomic models, then they really have to be substantially contributing to our understanding and ability to explain and grasp real macroeconomic processes. If not, they should – after somehow perhaps being able to sharpen our thoughts – be thrown into the waste-paper-basket (something the father of macroeconomics, Keynes, used to do), and not as today, being allowed to overrun our economics journals and giving their authors celestial academic prestige.

Krugman’s explications on this issue are really interesting also because they shed light on a kind of inconsistency in his art of argumentation. For years now, Krugman has repeatedly criticized mainstream economics for using too much (bad) mathematics and axiomatics in their model-building endeavours. But when it comes to defending his own position on various issues he usually himself ultimately falls back on the same kind of models. In his End This Depression Now — just to take one example — Paul Krugman maintains that although he doesn’t buy “the assumptions about rationality and markets that are embodied in many modern theoretical models, my own included,” he still find them useful “as a way of thinking through some issues carefully.”

When it comes to methodology and assumptions, Krugman obviously has a lot in common with the kind of model-building he otherwise criticizes. And as Rosenberg rightly notices:

When he accepts maximizing and equilibrium as the (only?) way useful economics is done Krugman makes a concession so great it threatens to undercut the rest of his arguments against New Classical economics.

Ist jeder Muslim ein Koran auf zwei Beinen?

15 Jan, 2019 at 18:39 | Posted in Politics & Society | Comments Off on Ist jeder Muslim ein Koran auf zwei Beinen?

 

10.0

15 Jan, 2019 at 18:26 | Posted in Varia | Comments Off on 10.0


Our youngest daughter was into gymnastics for many years, so I’ve seen how much practice and effort it takes to do things like this. Amazing performance!

On the​ emptiness of Bayesian probabilism

15 Jan, 2019 at 17:49 | Posted in Statistics & Econometrics | 1 Comment

unknownA major attraction of the personalistic [Bayesian] view is that it aims to address uncertainty that is not directly based on statistical data, in the narrow sense of that term​. Clearly much uncertainty is of this broader kind. Yet when we come to specific issues I believe that a snag in the theory emerges. To take an example that concerns me at the moment: what is the evidence that the signals from mobile telephones or transmission base stations are a major health hazard? Because such telephones are relatively new and the latency period for the development of, say, brain tumours is long the direct epidemiological evidence is slender; we rely largely on the interpretation of animal and cellular studies and to some extent on theoretical calculations about the energy levels that are needed to induce certain changes. What ​is the probability that conclusions drawn from such indirect studies have relevance for human health? Now I can elicit what my personal probability actually is at the moment, at least approximately. But that is not the issue. I want to know what my personal probability ought to be, partly because I want to behave sensibly and much more importantly because I am involved in the writing of a report which wants to be generally convincing. I come to the conclusion that my personal probability is of little interest to me and of no interest whatever to anyone else unless it is based on serious and so far as feasible explicit information. For example, how often have very broadly comparable laboratory studies been misleading as regards human health? How distant are the laboratory studies from a direct process affecting health? The issue is not to elicit how much weight I actually put on such considerations but how much I ought to put. Now of course in the personalistic approach having (good) information is better than having none but the point is that in my view the personalistic probability is virtually worthless for reasoned discussion​ unless it is based on information, often directly or indirectly of a broadly frequentist kind. The personalistic approach as usually presented is in danger of putting the cart before the horse.

David Cox

The nodal point here is that although Bayes’ theorem is mathematically unquestionable, that doesn’t qualify it as indisputably applicable to scientific questions. Science is not reducible to betting, and scientific inference is not a branch of probability theory. It always transcends mathematics. The unfulfilled dream of constructing an inductive logic of probabilism — the Bayesian Holy Grail — will always remain unfulfilled.

Bayesian probability calculus is far from the automatic inference engine that its protagonists maintain it is. That probabilities may work for expressing uncertainty when we pick balls from an urn, does not automatically make it relevant for making inferences in science. Where do the priors come from? Wouldn’t it be better in science if we did some scientific experimentation and observation if we are uncertain, rather than starting to make calculations based on often vague and subjective personal beliefs? People have a lot of beliefs, and when they are plainly wrong, we shall not do any calculations whatsoever on them. We simply reject them. Is it, from an epistemological point of view, really credible to think that the Bayesian probability calculus makes it possible to somehow fully assess people’s subjective beliefs? And are — as many Bayesians maintain — all scientific controversies and disagreements really possible to explain in terms of differences in prior probabilities? I’ll be dipped!

Keynes on the limits​ of econometric methods

14 Jan, 2019 at 20:20 | Posted in Statistics & Econometrics | 5 Comments

4388529Am I right in thinking that the method of multiple correlation analysis essentially depends on the economist having furnished, not merely a list of the significant causes, which is correct so far as it goes, but a complete list? For example, suppose three factors are taken into account, it is not enough that these should be in fact vera causa; there must be no other significant factor. If there is a further factor, not taken account of, then the method is not able to discover the relative quantitative importance of the first three. If so, this means that the method is only applicable where the economist is able to provide beforehand a correct and indubitably complete analysis of the significant factors. The method is one neither of discovery nor of criticism. It is a means of giving quantitative precision to what, in qualitative terms, we know already as the result of a complete theoretical analysis.

John Maynard Keynes

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