The problem of extrapolation

14 February, 2018 at 00:01 | Posted in Theory of Science & Methodology | 8 Comments

steelThere are two basic challenges that confront any account of extrapolation that seeks to resolve the shortcomings of simple induction. One challenge, which I call extrapolator’s circle, arises from the fact that extrapolation is worthwhile only when there are important limitations on what one can learn about the target by studying it directly. The challenge, then, is to explain how the suitability of the model as a basis for extrapolation can be established given only limited, partial information about the target … The second challenge is a direct consequence of the heterogeneity of populations studied in biology and social sciences. Because of this heterogeneity, it is inevitable there will be causally relevant differences between the model and the target population.

In economics — as a rule — we can’t experiment on the real-world target directly.  To experiment, economists therefore standardly construct ‘surrogate’ models and perform ‘experiments’ on them. To be of interest to us, these surrogate models have to be shown to be relevantly ‘similar’ to the real-world target, so that knowledge from the model can be exported to the real-world target. The fundamental problem highlighted by Steel is that this ‘bridging’ is deeply problematic​ — to show that what is true of the model is also true of the real-world target, we have to know what is true of the target, but to know what is true of the target we have to know that we have a good model  …

Most models in science are representations of something else. Models “stand for” or “depict” specific parts of a “target system” (usually the real world). A model that has neither surface nor deep resemblance to important characteristics of real economies ought to be treated with prima facie suspicion. How could we possibly learn about the real world if there are no parts or aspects of the model that have relevant and important counterparts in the real world target system? The burden of proof lays on the theoretical economists thinking they have contributed anything of scientific relevance without even hinting at any bridge enabling us to traverse from model to reality. All theories and models have to use sign vehicles to convey some kind of content that may be used for saying something of the target system. But purpose-built tractability assumptions — like, e. g., invariance, additivity, faithfulness, modularity, common knowledge, etc., etc. — made solely to secure a way of reaching deductively validated results in mathematical models, are of little value if they cannot be validated outside of the model.

All empirical sciences use simplifying or unrealistic assumptions in their modeling activities. That is (no longer) the issue – as long as the assumptions made are not unrealistic in the wrong way or for the wrong reasons.

Theories are difficult to directly confront with reality. Economists therefore build models of their theories. Those models are representations that are directly examined and manipulated to indirectly say something about the target systems.

There are economic methodologists and philosophers that argue for a less demanding view on modeling and theorizing in economics. And to some theoretical economists it is deemed quite enough to consider economics as a mere “conceptual activity” where the model is not so much seen as an abstraction from reality, but rather a kind of “parallel reality”. By considering models as such constructions, the economist distances the model from the intended target, only demanding the models to be credible, thereby enabling him to make inductive inferences to the target systems.

But what gives license to this leap of faith, this “inductive inference”? Within-model inferences in formal-axiomatic models are usually deductive, but that does not come with a warrant of reliability for inferring conclusions about specific target systems. Since all models in a strict sense are false (necessarily building in part on false assumptions) deductive validity cannot guarantee epistemic truth about the target system. To argue otherwise would surely be an untenable overestimation of the epistemic reach of surrogate models.

Models do not only face theory. They also have to look to the world. But being able to model a credible world, a world that somehow could be considered real or similar to the real world, is not the same as investigating the real world. Even though all theories are false, since they simplify, they may still possibly serve our pursuit of truth. But then they cannot be unrealistic or false in any way. The falsehood or unrealisticness has to be qualified (in terms of resemblance, relevance etc). At the very least, the minimalist demand on models in terms of credibility has to give away to a stronger epistemic demand of appropriate similarity and plausibility. One could of course also ask for a sensitivity or robustness analysis, but the credible world, even after having tested it for sensitivity and robustness, can still be a far way from reality – and unfortunately often in ways we know are important. Robustness of claims in a model does not per se give a warrant for exporting the claims to real world target systems.

Questions of external validity — the claims the extrapolation inference is supposed to deliver — are important. It can never be enough that models somehow are regarded as internally consistent. One always also has to pose questions of consistency with the data. Internal consistency without external validity is worth nothing.

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The arrow of time in a non-ergodic world

13 February, 2018 at 09:00 | Posted in Theory of Science & Methodology | 3 Comments

an end of certaintyFor the vast majority of scientists, thermodynamics had to be limited strictly to equilibrium. That was the opinion of J. Willard Gibbs, as well as of Gilbert N. Lewis. For them, irreversibility associated with unidirectional time was anathema …

I myself experienced this type of hostility in 1946 … After I had presented my own lecture on irreversible thermodynamics, the greatest expert in the field of thermodynamics made the following comment: ‘I am astonished that this young man is so interested in nonequilibrium physics. Irreversible processes are transient. Why not wait and study equilibrium as everyone else does?’ I was so amazed at this response that I did not have the presence of mind to answer: ‘But we are all transient. Is it not natural to be interested in our common human condition?’

Time is what prevents everything from happening at once. To simply assume that economic processes are ergodic and concentrate on ensemble averages — and hence in any relevant sense timeless — is not a sensible way for dealing with the kind of genuine uncertainty that permeates real-world economies.

Ergodicity and the all-important difference between time averages and ensemble averages are difficult concepts — so let me try to explain the meaning of these concepts by means of a couple of simple examples.

Let’s say you’re offered a gamble where on a roll of a fair die you will get €10  billion if you roll a six, and pay me €1 billion if you roll any other number.

Would you accept the gamble?

If you’re an economics student​ you probably would, because that’s what you’re taught to be the only thing consistent with being rational. You would arrest the arrow of time by imagining six different “parallel universes” where the independent outcomes are the numbers from one to six, and then weight them using their stochastic probability distribution. Calculating the expected value of the gamble – the ensemble average – by averaging on all these weighted outcomes you would actually be a moron if you didn’t take the gamble (the expected value of the gamble being 5/6*€0 + 1/6*€10 billion = €1.67 billion)

If you’re not an economist you would probably trust your common sense and decline the offer, knowing that a large risk of bankrupting one’s economy is not a very rosy perspective for the future. Since you can’t really arrest or reverse the arrow of time, you know that once you have lost the €1 billion, it’s all over. The large likelihood that you go bust weights heavier than the 17% chance of you becoming enormously rich. By computing the time average – imagining one real universe where the six different but dependent outcomes occur consecutively – we would soon be aware of our assets disappearing, and a fortiori that it would be irrational to accept the gamble.

Why is the difference between ensemble and time averages of such importance in economics? Well, basically, because when assuming the processes to be ergodic, ensemble and time averages are identical.

Assume we have a market with an asset priced at €100.​ Then imagine the price first goes up by 50% and then later falls by 50%. The ensemble average for this asset would be €100 – because we here envision two parallel universes (markets) where the asset price​ falls in one universe (market) with 50% to €50, and in another universe (market) it goes up with 50% to €150, giving an average of 100 € ((150+50)/2). The time average for this asset would be 75 € – because we here envision one universe (market) where the asset price first rises by 50% to €150, and then falls by 50% to €75 (0.5*150).

From the ensemble perspective nothing really, on average, happens. From the time perspective lots of things really, on average, happen. Assuming ergodicity there would have been no difference at all.

On a more economic-theoretical level, ​the difference between ensemble and time averages also highlights the problems concerning the neoclassical theory of expected utility.

When applied to the neoclassical theory of expected utility, one thinks in terms of “parallel universe” and asks what is the expected return of an investment, calculated as an average over the “parallel universe”? In our coin tossing example, it is as if one supposes that various “I” are tossing a coin and that the loss of many of them will be offset by the huge profits one of these “I” does. But this ensemble average does not work for an individual, for whom a time average better reflects the experience made in the “non-parallel universe” in which we live.

Time averages give​ a more realistic answer, where one thinks in terms of the only universe we actually live in, and ask what is the expected return of an investment, calculated as an average over time.

Since we cannot go back in time – entropy and the arrow of time make this impossible – and the bankruptcy option is always at hand (extreme events and “black swans” are always possible) we have nothing to gain from thinking in terms of ensembles.

Actual events follow a fixed pattern of time, where events are often linked in a multiplicative process (as e. g. investment returns with “compound interest”) which is basically non-ergodic.

Instead of arbitrarily assuming that people have a certain type of utility function – as in the neoclassical theory – time average considerations show that we can obtain a less arbitrary and more accurate picture of real people’s decisions and actions by basically assuming that time is irreversible. When are assets are gone, they are gone. The fact that in a parallel universe it could conceivably have been refilled, is​ of little comfort to those who live in the one and only possible world that we call the real world.

Our coin toss example can be applied to more traditional economic issues. If we think of an investor, we can basically describe his situation in terms of our coin toss. What fraction of his assets should an investor – who is about to make a large number of repeated investments – bet on his feeling that he can better evaluate an investment (p = 0.6) than the market (p = 0.5)? The greater the fraction, the greater is the leverage. But also – the greater is the risk. Letting p be the probability that his investment valuation is correct and (1 – p) is the probability that the market’s valuation is correct, it means that he optimizes the rate of growth on his investments by investing a fraction of his assets that is equal to the difference in the probability that he will “win” or “lose”. This means that he at each investment opportunity (according to the so-called Kelly criterion) is to invest the fraction of  0.6 – (1 – 0.6), i.e. about 20% of his assets (and the optimal average growth rate of investment can be shown to be about 2% (0.6 log (1.2) + 0.4 log (0.8))).

Time average considerations show that because we cannot go back in time, we should not take excessive risks. High leverage increases the risk of bankruptcy. This should also be a warning for the financial world, where the constant quest for greater and greater leverage – and risks – creates extensive and recurrent systemic crises. A more appropriate level of risk-taking is a necessary ingredient in a policy to come to curb excessive risk-taking​.

To understand real world “non-routine” decisions and unforeseeable changes in behaviour, ergodic probability distributions are of no avail. In a world full of genuine uncertainty — where real historical time rules the roost — the probabilities that ruled the past are not necessarily those that will rule the future.

Irreversibility can no longer be identified with a mere appearance​ that would disappear if we had perfect knowledge … Figuratively speaking, matter at equilibrium, with no arrow of time, is ‘blind,’ but with the arrow of time, it begins to ‘see’ … The claim that the arrow of time is ‘only phenomenological​l,’ or subjective, is therefore absurd. We are actually the children of the arrow of time, of evolution, not its progenitors.

Ilya Prigogine

Hur skiljer man på vetenskap och trams?

3 February, 2018 at 16:01 | Posted in Theory of Science & Methodology | Leave a comment

fransEmma Frans’ med rätta prisbelönta bok Larmrapporten är en rolig, kunnig och ack så nödvändig uppgörelse med allehanda pseudo-vetenskapligt trams som sköljer över oss i media nuförtiden. Inte minst i sociala media sprids en massa ‘alternativa fakta’ och nonsens.

Även om jag varmt rekommederat studenter, vänner och bekanta att läsa boken, kan jag dock inte låta bli att här påpeka att det finns en liten svaghet i boken. Det gäller behandlingen av evidens-baserad kunskap och då speciellt bilden av det som brukar kallas den vetenskapliga evidensens ‘gold standard’ — randomiserade kontrollerade studier (RCT).

Frans skriver:

gold-standard RCT är den typ av studier som överlag anses ha högst bevisvärde. Detta beror på att slumpen avgör vem som utsätts för interventionen och vem som får vara kontroll. Om studien är tillräckligt stor kommer slumpen se till att den enda betydelsefulla skillnaden mellan grupperna som jämförs är om de utsatts för interventionen eller inte. Om det senare går att se en skillnad mellan grupperna med avseende på utfallet så kan vi känna oss säkra på att detta beror på interventionen.

Detta är en rätt standardmässig presentation av vilka (påstådda) fördelar RCT har (bland dess förespråkare).

Problemet är bara att det ur strikt vetenskaplig synpunkt är fel!

Låt mig förklara varför med ett belysande exempel.

Continue Reading Hur skiljer man på vetenskap och trams?…

Mainstream economics gets the priorities wrong

20 January, 2018 at 17:46 | Posted in Theory of Science & Methodology | Comments Off on Mainstream economics gets the priorities wrong

There is something about the way economists construct their models nowadays that obviously doesn’t sit right.

significance_cartoonThe one-sided, almost religious, insistence on axiomatic-deductivist modelling as the only scientific activity worthy of pursuing in economics still has not given way to methodological pluralism based on ontological considerations (rather than formalistic tractability). In their search for model-based rigour and certainty, ‘modern’ economics has turned out to be a totally hopeless project in terms of real-world relevance

If macroeconomic models – no matter of what ilk –  build on microfoundational assumptions of representative actors, rational expectations, market clearing and equilibrium, and we know that real people and markets cannot be expected to obey these assumptions, the warrants for supposing that model-based conclusions or hypotheses of causally relevant mechanisms or regularities can be bridged to real-world target systems, are obviously non-justifiable. Incompatibility between actual behaviour and the behaviour in macroeconomic models building on representative actors and rational expectations microfoundations shows the futility of trying to represent real-world target systems with models flagrantly at odds with reality. As Robert Gordon once had it:

Rigor competes with relevance in macroeconomic and monetary theory, and in some lines of development macro and monetary theorists, like many of their colleagues in micro theory, seem to consider relevance to be more or less irrelevant.

The real harm done by Bayesianism

30 November, 2017 at 09:02 | Posted in Theory of Science & Methodology | 2 Comments

419Fn8sV1FL._SY344_BO1,204,203,200_The bias toward the superficial and the response to extraneous influences on research are both examples of real harm done in contemporary social science by a roughly Bayesian paradigm of statistical inference as the epitome of empirical argument. For instance the dominant attitude toward the sources of black-white differential in United States unemployment rates (routinely the rates are in a two to one ratio) is “phenomenological.” The employment differences are traced to correlates in education, locale, occupational structure, and family background. The attitude toward further, underlying causes of those correlations is agnostic … Yet on reflection, common sense dictates that racist attitudes and institutional racism must play an important causal role. People do have beliefs that blacks are inferior in intelligence and morality, and they are surely influenced by these beliefs in hiring decisions … Thus, an overemphasis on Bayesian success in statistical inference discourages the elaboration of a type of account of racial disadavantages that almost certainly provides a large part of their explanation.

For all scholars seriously interested in questions on what makes up a good scientific explanation, Richard Miller’s Fact and Method is a must read. His incisive critique of Bayesianism is still unsurpassed.

wpid-bilindustriella-a86478514bOne of yours truly’s favourite ‘problem situating lecture arguments’ against Bayesianism goes something like this: Assume you’re a Bayesian turkey and hold a nonzero probability belief in the hypothesis H that “people are nice vegetarians that do not eat turkeys and that every day I see the sunrise confirms my belief.” For every day you survive, you update your belief according to Bayes’ Rule

P(H|e) = [P(e|H)P(H)]/P(e),

where evidence e stands for “not being eaten” and P(e|H) = 1. Given that there do exist other hypotheses than H, P(e) is less than 1 and a fortiori P(H|e) is greater than P(H). Every day you survive increases your probability belief that you will not be eaten. This is totally rational according to the Bayesian definition of rationality. Unfortunately — as Bertrand Russell famously noticed — for every day that goes by, the traditional Christmas dinner also gets closer and closer …

For more on my own objections to Bayesianism, see my Bayesianism — a patently absurd approach to science and One of the reasons I’m a Keynesian and not a Bayesian.

Emma Frans och konsten att skilja vetenskap från trams

24 November, 2017 at 19:15 | Posted in Theory of Science & Methodology | 2 Comments

fransEmma Frans’ med rätta prisbelönta bok Larmrapporten är en rolig, kunnig och ack så nödvändig uppgörelse med allehanda pseudo-vetenskapligt trams som sköljer över oss i media nuförtiden. Inte minst i sociala media sprids en massa ‘alternativa fakta’ och nonsens.

Även om jag varmt rekommederat studenter, vänner och bekanta att läsa boken, kan jag dock inte låta bli att här — bland mestadels akademiskt skolade läsare — påpeka att det finns en liten svaghet i boken. Det gäller behandlingen av evidens-baserad kunskap och då speciellt bilden av det som brukar kallas den vetenskapliga evidensens ‘gold standard’ — randomiserade kontrollerade studier (RCT).

Frans skriver:

gold-standard RCT är den typ av studier som överlag anses ha högst bevisvärde. Detta beror på att slumpen avgör vem som utsätts för interventionen och vem som får vara kontroll. Om studien är tillräckligt stor kommer slumpen se till att den enda betydelsefulla skillnaden mellan grupperna som jämförs är om de utsatts för interventionen eller inte. Om det senare går att se en skillnad mellan grupperna med avseende på utfallet så kan vi känna oss säkra på att detta beror på interventionen.

Detta är en rätt standardmässig presentation av vilka (påstådda) fördelar RCT har (bland dess förespråkare).

Problemet är bara att det ur strikt vetenskaplig synpunkt är fel!

Låt mig förklara varför jag anser detta med ett belysande exempel från skolvärlden.

Continue Reading Emma Frans och konsten att skilja vetenskap från trams…

Randomization — a philosophical device gone astray

23 November, 2017 at 10:30 | Posted in Theory of Science & Methodology | 1 Comment

When giving courses in the philosophy of science yours truly has often had David Papineau’s book Philosophical Devices (OUP 2012) on the reading list. Overall it is a good introduction to many of the instruments used when performing methodological and science theoretical analyses of economic and other social sciences issues.

Unfortunately, the book has also fallen prey to the randomization hype that scourges sciences nowadays.

philosophical-devices-proofs-probabilities-possibilities-and-sets The hard way to show that alcohol really is a cause of heart disease is to survey the population … But there is an easier way … Suppose we are able to perform a ‘randomized experiment.’ The idea here is not to look at correlations in the population at large, but rather to pick out a sample of individuals, and arrange randomly for some to have the putative cause and some not.

The point of such a randomized experiment is to ensure that any correlation between the putative cause and effect does indicate a causal connection. This works​ because the randomization ensures that the putative cause is no longer itself systematically correlated with any other properties that exert a causal influence on the putative effect … So a remaining correlation between the putative cause and effect must mean that they really are causally connected.

The problem with this simplistic view on randomization is that the claims made by Papineau on behalf of randomization are both exaggerated and invalid:

• Even if you manage to do the assignment to treatment and control groups ideally random, the sample selection certainly is — except in extremely rare cases — not random. Even if we make a proper randomized assignment, if we apply the results to a biased sample, there is always the risk that the experimental findings will not apply. What works ‘there,’ does not work ‘here.’ Randomization a fortiori does not ‘guarantee ‘ or ‘ensure’ making the right causal claim. Although randomization may help us rule out certain possible causal claims, randomization per se does not guarantee anything!

• Even if both sampling and assignment are made in an ideal random way, performing standard randomized experiments only give you averages. The problem here is that although we may get an estimate of the ‘true’ average causal effect, this may ‘mask’ important heterogeneous effects of a causal nature. Although we get the right answer of the average causal effect being 0, those who are ‘treated’  may have causal effects equal to -100 and those ‘not treated’ may have causal effects equal to 100. Contemplating being treated or not, most people would probably be interested in knowing about this underlying heterogeneity and would not consider the average effect particularly enlightening.

• Since most real-world experiments and trials build on performing a single randomization, what would happen if you kept on randomizing forever, does not help you to ‘ensure’ or ‘guarantee’ that you do not make false causal conclusions in the one particular randomized experiment you actually do perform. It is indeed difficult to see why thinking about what you know you will never do, would make you happy about what you actually do.

Randomization is not a panacea — it is not the best method for all questions and circumstances. Papineau and other proponents of randomization make claims about its ability to deliver causal knowledge that are simply wrong. There are good reasons to be sceptical of the now popular — and ill-informed — view that randomization is the only valid and best method on the market. It is not.

Top 10 RCT critiques

22 November, 2017 at 15:17 | Posted in Theory of Science & Methodology | Comments Off on Top 10 RCT critiques

top-10-retail-news-thumb-610xauto-79997-600x240-1

•Basu, Kaushik (2014) Randomisation, Causality and the Role of Reasoned Intuition

Randomized experiments — a dangerous idolatry

21 November, 2017 at 19:08 | Posted in Theory of Science & Methodology | 1 Comment

Hierarchy-of-EvidenceNowadays many mainstream economists maintain that ‘imaginative empirical methods’ — especially randomized experiments (RCTs) — can help us to answer questions concerning the external validity of economic models. In their view, they are, more or less, tests of ‘an underlying economic model’ and enable economists to make the right selection from the ever-expanding ‘collection of potentially applicable models.’

It is widely believed among economists that the scientific value of randomization — contrary to other methods — is totally uncontroversial and that randomized experiments are free from bias. When looked at carefully, however, there are in fact few real reasons to share this optimism on the alleged ’experimental turn’ in economics. Strictly seen, randomization does not guarantee anything.

Assume that you are involved in an experiment where we examine how the work performance of Chinese workers (A) is affected by a specific ‘treatment’ (B). How can we extrapolate/generalize to new samples outside the original population (e.g. to the US)? How do we know that any replication attempt ‘succeeds’? How do we know when these replicated experimental results can be said to justify inferences made in samples from the original population? If, for example, P(A|B) is the conditional density function for the original sample, and we are interested in doing an extrapolative prediction of E [P(A|B)], how can we know that the new sample’s density function is identical with the original? Unless we can give some really good argument for this being the case, inferences built on P(A|B) is not really saying anything on that of the target system’s P(A|B).

External validity and extrapolation are founded on the assumption that we could make inferences based on P(A|B) that is exportable to other populations for which P(A|B) applies. Sure, if one can convincingly show that P and P’ are similar enough, the problems are perhaps surmountable. But arbitrarily just introducing functional specification restrictions of the type invariance or homogeneity, is, at least for an epistemological realist far from satisfactory.

Many ‘experimentalists claim that it is easy to replicate experiments under different conditions and therefore a fortiori easy to test the robustness of experimental results. But is it really that easy? Population selection is almost never simple. Had the problem of external validity only been about inference from sample to population, this would be no critical problem. But the really interesting inferences are those we try to make from specific experiments to specific real-world structures and situations that we are interested in understanding or (causally) to explain. And then the population problem is more difficult to tackle.

In randomized trials the researchers try to find out the causal effects that different variables of interest may have by changing circumstances randomly — a procedure somewhat (‘on average’) equivalent to the usual ceteris paribus assumption.

Besides the fact that ‘on average’ is not always ‘good enough,’ it amounts to nothing but hand waving to simpliciter assume, without argumentation, that it is tenable to treat social agents and relations as homogeneous and interchangeable entities.

Randomization is used to basically allow the econometrician to treat the population as consisting of interchangeable and homogeneous groups (‘treatment’ and ‘control’). The regression models one arrives at by using randomized trials tell us the average effect that variations in variable X has on the outcome variable Y, without having to explicitly control for effects of other explanatory variables R, S, T, etc., etc. Everything is assumed to be essentially equal except the values taken by variable X.

In a usual regression context one would apply an ordinary least squares estimator (OLS) in trying to get an unbiased and consistent estimate:

Y = α + βX + ε,

where α is a constant intercept, β a constant ‘structural’ causal effect and ε an error term.

The problem here is that although we may get an estimate of the ‘true’ average causal effect, this may ‘mask’ important heterogeneous effects of a causal nature. Although we get the right answer of the average causal effect being 0, those who are ‘treated'( X=1) may have causal effects equal to – 100 and those ‘not treated’ (X=0) may have causal effects equal to 100. Contemplating being treated or not, most people would probably be interested in knowing about this underlying heterogeneity and would not consider the OLS average effect particularly enlightening.

Limiting model assumptions in economic science always have to be closely examined since if we are going to be able to show that the mechanisms or causes that we isolate and handle in our models are stable in the sense that they do not change when we ‘export’ them to our ‘target systems,’ we have to be able to show that they do not only hold under ceteris paribus conditions and a fortiori only are of limited value to our understanding, explanations or predictions of real economic systems.

Most ‘randomistas’ underestimate the heterogeneity problem. It does not just turn up as an external validity problem when trying to ‘export’ regression results to different times or different target populations. It is also often an internal problem to the millions of regression estimates that economists produce every year.

‘Ideally controlled experiments’ tell us with certainty what causes what effects — but only given the right ‘closures.’ Making appropriate extrapolations from (ideal, accidental, natural or quasi) experiments to different settings, populations or target systems, is not easy. “It works there” is no evidence for “it will work here”. Causes deduced in an experimental setting still have to show that they come with an export-warrant to the target population/system. The causal background assumptions made have to be justified, and without licenses to export, the value of ‘rigorous’ and ‘precise’ methods — and ‘on-average-knowledge’ — is despairingly small.

the-right-toolRCTs usually do not provide evidence that the results are exportable to other target systems. The almost religious belief with which its propagators portray it, cannot hide the fact that RCTs cannot be taken for granted to give generalizable results. That something works somewhere is no warranty for us to believe it to work for us here or even that it works generally.

The present RCT idolatry is dangerous. Believing there is only one really good evidence-based method on the market — and that randomization is the only way to achieve scientific validity — blinds people to searching for and using other methods that in many contexts are better. RCTs are simply not the best method for all questions and in all circumstances. Insisting on using only one tool often means using the wrong tool.

Science and reason

29 October, 2017 at 09:44 | Posted in Theory of Science & Methodology | 2 Comments

scrivenTrue scientific method is open-minded, self-critical, flexible. Scientists are, in short, not as reasonable as they would like to ​think themselves. The great scientists are often true exceptions; they are nearly always attacked by their colleagues for their revolutionary ideas, not by using the standards of reason, but just by appealing​ to prejudices then current.​ Being reasonable takes great skill and great​ sensitivity to the difference between “well-supported” and “widely accepted.” It also takes great courage, because it seldom corresponds to being popular.

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