Archive for Science

Olympus at work [Nature snapshot]

Posted in Books, pictures, Travel, University life with tags , , , , , , , on June 28, 2020 by xi'an


Posted in Books, pictures, Statistics, Travel with tags , , , , , , , , on March 20, 2020 by xi'an

The paper “The effect of travel restrictions on the spread of the 2019 novel coronavirus (COVID-19) outbreak”, published in Science on 06 March by Matteo Chinazzi and co-authors, considers the impact of travel restriction in Wuhan on the propagation of the virus. (Terrible graph by the way since the overall volume of traffic dropped considerably after the ban.)

“The travel quarantine of Wuhan delayed the overall epidemic progression by only 3 to 5 days in Mainland China, but has a more marked effect at the international scale, where case importations were reduced by nearly 80% until mid February.”

They use a SLIR (susceptible-latent-infectious-removed) pattern of transmission, along with a travel flow network based on 2019 air and ground travel statistics, resorting to ABC for approximating the posterior distribution of the basic reproductive number. It is however unclear to me that the model is particularly accurate at the levels of the transmission pattern (which now seems to occur much earlier than when the symptoms appear) and of the detection rates (which vary greatly from one place to another).

Yikes! “AI can predict which criminals may break laws again better than humans”

Posted in Books, pictures, Statistics with tags , , , , , , , on February 28, 2020 by xi'an

Science (the journal!) has this heading on its RSS feed page, which makes me wonder if they have been paying any attention to the well-documented issues with AI driven “justice”.

“…some research has given reason to doubt that algorithms are any better at predicting arrests than humans are.”

Among other issues, the study compared volunteers with COMPAS‘ or LSI-R predictive abilities for predicting violent crime behaviour, based on the same covariates. Volunteers, not experts! And the algorithms are only correct 80% of the time which is a terrible perfomance when someone’s time in jail depends on it!

“Since neither humans nor algorithms show amazing accuracy at predicting whether someone will commit a crime two years down the line, “should we be using [those forecasts] as a metric to determine whether somebody goes free?” Farid says. “My argument is no.””

science under attack [it only gets worse #1074]

Posted in Kids, pictures, Travel, University life with tags , , , , , , , , , , , on January 6, 2020 by xi'an

A chilling overview by the New York Times on the permanent and concerted attacks by the Trump administration on science and the scientific duties of the U.S. Government. [This post was written a week ago, before a much scarier and literal as well as extra-judicial attack took place.]

“Political appointees have shut down government studies, reduced the influence of scientists over regulatory decisions and in some cases pressured researchers not to speak publicly. The administration has particularly challenged scientific findings related to the environment and public health opposed by industries such as oil drilling and coal mining. It has also impeded research around human-caused climate change, which President Trump has dismissed despite a global scientific consensus.”

“The administration’s efforts to cut certain research projects also reflect a longstanding conservative position that some scientific work can be performed cost-effectively by the private sector, and taxpayers shouldn’t be asked to foot the bill.”

“…some of the Trump administration’s moves, like a policy to restrict certain academics from the E.P.A.’s Science Advisory Board or the proposal to limit the types of research that can be considered by environmental regulators, “mark a sharp departure with the past.” Rather than isolated battles between political officials and career experts, these moves are an attempt to legally constrain how federal agencies use science in the first place.”

“In addition to shutting down some programs, there have been notable instances where the administration has challenged established scientific research. Early on, as it started rolling back regulations on industry, administration officials began questioning research findings underpinning those regulations (…) Many top government positions, including at the E.P.A. and the Interior Department, are now occupied by former lobbyists connected to the industries that those agencies oversee.”

gender gaps

Posted in Statistics, University life with tags , , , , , , , , , , on March 31, 2018 by xi'an

Two of my colleagues [and co-authors] at Dauphine, Elyès Jouini and Clotilde Napp, published a paper in Science last week (and an associated tribune in Le Monde which I spotted first) about explaining differences in national gender inequalities in maths (as measured by PISA) in terms of the degree of overall inequality in the respective countries. Gaps in the highest maths performer sex ratio. While I have no qualm about the dependency or the overall statistical cum machine learning analysis (supported by our common co-author Jean-Michel Marin), and while I obviously know nothing about the topic!, I leisurely wonder at the cultural factor (which may also partly explain for the degree of inequality) when considering that the countries at the bottom of the above graphs are rather religious (and mostly catholic). I also find it most intriguing that the gender gap is consistently reversed when considering higher performer sex ratio for reading, because mastering the language should be a strong factor in power structures and hence differences therein should also lead to inequalities…