Category Archives: Real life

Pareto principle in train travel

The moral of this story is don’t travel with me.  Last week, I wrote about my train being delayed by someone pulling the emergency handle before we got to the end of the platform in Liverpool [see ‘Stopped in Lime Street’ on June 26th, 2019].  Four days later, I was once again on a late afternoon train to London waiting for it to leave Lime Street station.  This time we didn’t even get started before the train manager announced that a road vehicle had hit a bridge between Crewe and Liverpool; and, so we were being held in Liverpool for an unknown period of time.  I sent a message to my family telling them about the delay and one, an engineer, replied that I was ‘hitting the low frequency failure modes on the service quality pareto’.  The Pareto principle is also known as the 80/20 principle.  I first encountered it when I was working at the University of Sheffield and the Vice-Chancellor,  Professor Gareth Roberts, used it to describe the distribution of research output in academic departments, i.e., 80% of research was produced by 20% of the professors.  In service maintenance, it is assumed that 80% of service interruptions are caused by 20% of the possible failure modes.  Hence, if you can address the correct 20% of failure modes then you will prevent 80% of the service interruptions, which is an efficient use of your resources.  The remaining, unaddressed failure modes are likely to occur infrequently and, hence, can be described as low frequency modes; including passengers pulling emergency handles or people driving vehicles into bridges.

How do you drive into a bridge and block the main railway lines between London and the north-west of England?  Perhaps the driver was using their smart phone which was not smart enough to warn them of the impending collision with the bridge.  So, there’s a new product for someone to develop: a smartphone app that connects to dashboard camera in your vehicle and warns you of impending collisions, or better still just drives the vehicle for you.  Yes, I know some vehicles come with all of this installed but not everyone is driving the latest model; so, a retro-fit system should sell well and protect train passengers from unexpected delays caused by road vehicles damaging rail infrastructure.

By the way, the 14:47 to London magically became the 15:47 to London and left on time!

Meta-knowledge: knowledge about knowledge

As engineers, we like to draw simple diagrams of the systems that we are attempting to analyse because most of us are pictorial problem-solvers and recording the key elements of a problem in a sketch helps us to identify the important issues and select an appropriate solution procedure [see ‘Meta-representational competence’ on May 13th, 2015].  Of course, these simple representations can be misleading if we omit parameters or features that dominate the behaviour of the system; so, there is considerable skill in idealising a system so that the analysis is tractable, i.e. can be solved.  Students find it especially difficult to acquire these skills [see ‘Learning problem-solving skills‘ on October 24th, 2018] and many appear to avoid drawing a meaningful sketch even when examinations marks are allocated to it [see ‘Depressed by exams‘ on January 31st, 2018].  Of course, in thermodynamics it is complicated by the entropy of the system being reduced when we omit parameters in order to idealise the system; because with fewer parameters to describe the system there are fewer microstates in which the system can exist and, hence according to Boltzmann, the entropy will be lower [see ‘Entropy on the brain‘ on November 29th, 2017].  Perhaps this is the inverse of realising that we understand less as we know more.  In other words, as our knowledge grows it reveals to us that there is more to know and understand than we can ever hope to comprehend [see ‘Expanding universe‘ on February 7th, 2018]. Is that the second law of thermodynamics at work again, creating more disorder to counter the small amount of order achieved in your brain?

Image: Sketch made during an example class

Knowledge explosions

Photo credit: Tom

When the next cohort of undergraduate students were born, Wikipedia had only just been founded [January 2001] and Google had been in existence for just over a decade [since 1998].  In their lifetime, the number of articles on Wikipedia has grown to nearly 6 million in the English language, which is equivalent to 2,500 print volumes of the Encyclopedia Britannica, and counting all language editions there are 48 million articles.  When Leonardo Da Vinci was born in 1452, Johan Gutenberg had just published his first Bible using moveable type.  By the time Leonardo Da Vinci was 20 years old, about 15 million books had been printed which was more than all of the scribes in Europe had produced in the previous 1500 years.  Are these comparable explosions in the availability of knowledge?  The proportion of the global population that is literate has changed dramatically from about 2%, when Leonardo was alive, to over 80% today which probably makes the arrival of the internet, Wikipedia and other online knowledge bases much more significant than the invention of the printing press.

Today what matters is not what you know but what you can do with the knowledge because access to the internet via your smart phone has made memorisation redundant.

Pluralistic ignorance

This semester I am teaching an introductory course in Thermodynamics to undergraduate students using a blended learning approach [see ‘Blended learning environments‘ on November 14th, 2018].  The blend includes formal lectures, example classes, homework assignments, assessed coursework questions and an on-line course, which I delivered as a MOOC a couple of years ago [see ‘Engaging learners on-line‘ on May 25th, 2016].  It is not unusual in a large class, nearly two hundred students this year, that no one asks questions during the lecture; although, at the end of each lecture and example class, a small group of students with questions always forms.  The on-line course has extensive opportunities for asking questions and discussing issues with the instructor and fellow learners.  These opportunities  were used heavily when the course was offered as a MOOC  with 6600 comments posted or 1 every 7.7 minutes!  However, this year the undergraduates have not made any on-line comments and it was a similar situation last year.  Is this a case of pluralistic ignorance?  The term was coined by psychologists Daniel Katz and Floyd Henry Allport in 1931 to describe students who pretend to understand everything explained in class and don’t ask any questions because they believe everyone else in the class has understood everything and they don’t want to damage their reputation with their peers.  Perhaps we have all done it and been very grateful when someone has asked the question that we wanted to ask but did not dare.  Would be it ethical to pretend to be a student and post questions on-line that I know from the MOOC they are likely to want to ask?


Patterson EA, Using everyday engineering examples to engage learners on a massive open online course, IJ Mechanical Engineering Education, in press.

Katz D & Allport FH, Students’ attitude, Syracuse, NY: Craftsmann, 1931.

Origgi G, Reputation: what it is and why it matters, Princeton, NJ: Princeton University Press, 2018.

Image: Author speaking at National Tsing Hua University, Taiwan