Upcoming seminars

Friday, February 23, 11:00

Ivana Malenica
Wojcicki Troper HDSI Fellow, Department of Statistics, Harvard University
Personalized Decision-Making in Highly Dependent Settings

Effective management of emerging and existing epidemics requires strategic decisions on where, when, and to whom interventions should be applied. However, personalized decision-making in infectious disease applications introduces new and unique statistical challenges. For instance, the individuals at risk of infection are unknown, the true outcome of interest (positive infection status) is often a latent variable, and the presence of complex dependence reduces data to a single observation. In this work, we investigate an adaptive sequential design under latent outcome structures and unspecified dependence through space and time. The statistical problem is addressed within a nonparametric model that respects the unknown dependence structure. I will begin by formalizing a treatment allocation strategy that utilizes up-to-date data to inform who is at risk of infection in real-time, with favorable theoretical properties. The optimal allocation strategy, or optimal policy, maximizes the mean latent outcome under a resource constraint. The proposed estimator learns the optimal policy over time and exploits the double-robust structure of the efficient influence function of the target parameters of interest. In the second part of the talk, I will present the study of data-adaptive inference on the mean under the optimal policy, where the target parameter adapts over time in response to the observed data (state of the epidemic). Lastly, I present a novel paradigm in nonparametric efficient estimation particularly suited for target parameters with complex dependence.

Wednesday, April 24, 15:15

Richard Gill
Leiden University
A tale of two Lucys

Lucia de Berk, a Dutch nurse, was arrested in 2001, and tried and convicted of serial murder of patients in her care. At a lower court the only hard evidence against her was the result of a probability calculation: the chance that she was present at so many suspicious deaths and collapses in the hospitals where she had worked was 1 in 342 million. During appeal proceedings at a higher court, the prosecution shifted gears and gave the impression that there was now hard evidence that she had killed one baby. Having established that she was a killer and a liar (she claimed innocence) it was not difficult to pin another 9 deaths and collapses on her. No statistics were needed any more. In 2005 the conviction was confirmed by the supreme court. But at the same time, some whistleblowers started getting attention from the media. A long fight for the hearts and minds of the public, and a long fight to have the case reopened (without any new evidence - only new scientific interpretation of existing evidence) began and ended in 2010 with Lucia’s complete exoneration. A number of statisticians played a big role in that fight. The idea that the conviction was purely based on objective scientific evidence was actually an illusion. This needed to be explained to journalists and to the public. And the judiciary needed to be convinced that something had to be done about it.

Lucy Letby, an English nurse, was arrested in 2020 for murder of a large number of babies at a hospital in Chester, UK, in Jan 2015-June 2016. Her trial started in 2022 and took 10 months. She was convicted and given a whole life sentence in 2023.

In my opinion, the similarities between the two cases are horrific. Again there is statistical evidence: a cluster of unexplained bad events, and Lucy was there every time; there is apparently irrefutable scientific evidence for two babies; and just like with Lucia de Berk, there are some weird personal and private writings which can be construed as a confession. For many reasons, the chances of a fair retrial for Lucy Letby are very thin indeed, but I am convinced she is innocent and that her trial was grossly unfair. I will try to convince you, too.

I predict that it will take between 6 and 12 years before she is exonerated.

Map of CSS

You can find CSS next to the Botanical Garden, 5 minutes from Nørreport station.

Meeting room 5.2.46 is the library of the Biostatistics section, located in building 5, 2nd floor, room 46. See the map below for directions inside CSS.