Sunday, August 7, 2011

Green IT Swiss Data Center presentation

Here is a short presentation on a relatively new data center in the west of Zurich that is designed to be green and secure.  More information at, and the language can be changed to English in the upper right corner.

US Grade Inflation Study

A recent study has examined the prevalence of grade inflation at US universities over the last 100 years or so, and has found some identifiable patterns. The chart below shows the increase in grades between various types of schools in the primary colors, with the grey representing (unnamed individual schools).


What is clear is that there was a huge increase in grade in crease in the 60’s and then a steady increase over  the last 30 years of so. From the study

The rise in grades in the 1960s correlates with the social upheavals of the Vietnam War. It was followed by a decade
period of static to falling grades. The cause of the renewal of grade inflation, which began in the 1980s and has yet to
end, is subject to debate, but it is difficult to ascribe this rise in grades to increases in student achievement. Students’ entrance test scores have not increased (College Board, 2007), students are increasingly disengaged from their studies (Saenz et al., 2007), and the literacy of graduates has declined (Kutner et al., 2006). A likely influence is the emergence of the now common practice of requiring student-based evaluations of college teachers. Whatever the cause, colleges and universities are on average grading easier than ever before.

Further science and engineering students are graded more harshly than their fellow students in liberal arts degrees.

A 10% Tipping Point Threshold

Scientists at Rensselaer Polytechnic Institute have recently published research into social networks which indicates  that when just 10 percent of a network steadfastly holds a given belief, then that belief will eventually be adopted by the majority of the society. These group of 10% “believers” are referred to as a committed minority.

Even though the research has produced quite a bit of press (see here and here for example) it is a little difficult to say how the result was arrived at. The abstract of the paper states that

We show how the prevailing majority opinion in a population can be rapidly reversed by a small fraction p of randomly distributed committed agents who consistently proselytize the opposing opinion and are immune to influence. Specifically, we show that when the committed fraction grows beyond a critical value pc≈10%, there is a dramatic decrease in the time Tc taken for the entire population to adopt the committed opinion. In particular, for complete graphs we show that when p<pc, Tc~exp[α(p)N], whereas for p>pc, Tc~lnN. We conclude with simulation results for Erdős-Rényi random graphs and scale-free networks which show qualitatively similar behavior.

It seems that they are using a model for the spread of opinion overlayed on various network topologies, starting with the complete graph (everyone knows everyone), then scale free, and a simulation of a random graph process. The results are strengthened by finding the 10% threshold present in each topology. Even so, the following graph was not that informative for me.


I think I will have to wait get a copy of the paper to make full sense of the result. Reported in Freakanomics.

Friday, August 5, 2011

iPhone Passcode Bias

An informal study from collecting just over 204,000 iPhone passcodes, produced the graphic below on the top ten most common passcodes


The author concludes that

Formulaic passwords are never a good idea, yet 15% of all passcode sets were represented by only 10 different passcodes (out of a possible 10,000). The implication? A thief (or just a prankster) could safely try 10 different passcodes on your iPhone without initiating the data wipe. With a 15% success rate, about 1 in 7 iPhones would easily unlock--even more if the intruder knows the users’ years of birth, relationship status, etc.

DIPK Graphic

From Flowing Data

Mark Johnstone uses a cake metaphor to represent data, presentation, and what you gain.

Don’t like the last shot for knowledge. Perhaps lots of smaller cakes?