Statistical estimation by imitation

Parameter estimation in a subcritical percolation model with colouring, or cross-contamination rate estimation for microfluidics

We have just published a research paper1 about a nice combination of statistics and applied probability theory. The story opens with a novel mathematical model to quantify unwanted cross-contamination within lab-on-a-chip microfluidic devices. We apply the method of simulated moments (MSM) to estimate the parameters of the model. This method uses computer simulation with many different parameter proposals until the simulated data is close enough to the observed data. Our main contribution is that we prove the statistical consistency (`correctness’) of this method. Proving that the estimate will converge with probability 1 to the true parameter value as the sample size tends to infinity was a challenge because of the dependence among our random sample’s variables.

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The price of moving to permanent summertime

The result of the European Commission’s Public Consultation on summertime arrangements was released today. In my opinion European Commission President Jean-Claude Juncker and German Chancellor Angela Merkel are reading too much into the non-binding and non-representative result. At this point, the realistic question to formulate would be: a) would you accept a time zone boundary splitting Western Europe as the price of ending the biannual clock changes, or b) do you prefer the current arrangement?

The consultation

The European Commission held a public consultation from 4th July until 16th August (6 weeks) to find out what the European citizens and stakeholders thought about the current system of daylight saving time. I really wonder if they achieved their goal. Continue reading

Wie aus 6 Stellen ich weiß gar nicht mehr wieviele werden

Die Geschichte entfaltet sich an der Rheinischen Friedrich-Wilhelms-Universität Bonn vor meinen Augen wie ein car crash in slow motion. Sie zeigt Probleme auf, die symptomatisch für den gesamten Arbeitsmarkt im deutschen Hochschulwesen sind. Die Schwierigkeiten mit befristeten Stellen, die NachwuchsforscherInnen bewältigen müssen, um am universitären Arbeitsmarkt Fuß fassen zu können, sind hinlänglich bekannt. Die bizarren Anreize der Beteiligten führen zu langsamer Auswertung der Bewerbungen und ausgeschriebene Stellen gehen vorübergehend, aber für lange Zeitdauer, verloren.

Ich will nicht mehr schweigen. Ich habe überlegt, ob ich auf Englisch oder auf Deutsch nicht mehr schweigen soll. Ich habe mich für Deutsch entschieden, damit Entscheidungsträger (auch in der Wissenschaftspolitik) die Probematik als ihre eigene annehmen werden.

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Santa’s Christmas delivery route revealed

Data visualisation meets children’s curiosity. We immerse ourselves in geoinformatics to find out how postal services in the USA, in Germany and in Hungary carved their countries into mosaics of postal code areas. Visually striking maps emerge from the opaque depths of numerical data.

Whoever still sends letters by post will notice that addresses closest to you share your postal code or differ only slightly, but opposite corners of your country will have very different codes. How do postal services cover countries with postal codes?

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Non-minimum-phase dynamics in an inflammation model

Inflammation is the innate immune system’s response to tissue damage caused by trauma or infection. Thinking about it as the quickly receding rash after an insect bite detracts from the major antagonistic role it plays in medicine. As Baldur Tumi Baldursson of the National University Hospital of Iceland put it, `I tell my students, your work is inflammation. Practically all of internal medicine is just fighting inflammation.’

Inflammation is a complex process involving different cell types, mediator molecules and changes in the permeability of capillaries and affected tissue. This reaction has to be ramped up quickly to defend our body, but it must also be kept under strict control to prevent immune cells causing tissue damage themselves. On occasion, things go wrong and a patient is left with chronic, abnormal inflammation: inflammatory bowel disease, coeliac disease or rheumatoid arthritis are a few debilitating examples.

A mathematical model of inflammation control

These notes extend the findings of three researchers from Britain—Joanne Dunster (Reading), Helen Byrne (Oxford) and John King (Nottingham)—using control theoretical insights, and perhaps contribute a new aspect to our understanding of the problem. Their 2014 paper1 drew attention to a shift from understanding inflammation resolution as a passive process to an active, anti-inflammatory mechanism. Continue reading

La La Land: a peer review

This weekend I saw the critically acclaimed new Hollywood musical, La La Land. I can warmly recommend it to my generation of nomadic, globetrotting, aspiring, bright-eyed and bushy-tailed academic scientists. It’s touching.

la_la_land

SPOILER ALERT: My clumsy words will completely spoil your enjoyment whether you’re planning to watch it or have already done so. Continue reading

Music cognition: probing the mind with music

What can you learn about a person from what music they like? Can you expect a difference in predisposition between those who prefer upbeat music versus those who like melancholic music? Do people with a taste for complex music have better cognitive skills, or is it a learned taste that results from devoting more time to the subject, or something else? Can a music streaming service make money through targeted advertising based solely on music preferences? Following from that, should we guard our musical taste closely? What might a future adversary infer about ourselves from our taste in music? Is it or will it be possible to scientifically predict which songs will be hits? If yes, can this capability be used during composition already?

I jumped the gun here by starting with the inverse (the inference) problem. The direct question is: do personality traits influence preferences for certain musical styles? This statistical framing assumes that there are hidden variables describing our personality and musical preferences are their functions, which can be observed. We will see that they do correlate.

Why do people differ so much in what music they like? More fundamentally, why do we like music? It seems most everyone likes music. Does this affection give us an evolutionary advantage, or is it just a neutral side effect of something that is advantageous? What percentage of us don’t like music? Are they a small minority, as social convention leads us to believe, or is there actually a silent majority for whom music is a nuisance? If they were a rarity, perhaps they are interesting subjects for psychological studies. How does rhythmic music suck many of us in and make us move with the beat? Shouldn’t we be better at controlling our bodies, at jamming such stimuli? Or is jamming more costly for some minds than moving with the rhythm? Continue reading