Where does that data come from?

Graph from the US National Snow and Ice Data Centre showing the extent of Arctic Sea Ice at the end of August 2013.

Good news! As the graph above shows, it looks like Arctic Sea Ice has not collapsed this year as it did in 2012. The graph below shows projections based on previous seasons and it seems very unlikely that sea ice extent will fall much further in the last month of the ‘melt season’. Excellent.

Graph from the US National Snow and Ice Data Centre showing the predicted extent of Arctic Sea Ice from now to the end of the melt season. The red line at the bottom shows the minimum value reached last year.

This excellent page at the US National Snow and Ice Data Centre shows some of the details behind these summary graphs and discusses in detail the difference between weather patterns this year and last.

But although this data is relatively simple to understand, it is not at all obvious what exactly is being measured! And just where does this data come from anyway!

Many regions of the Arctic have partially-melted ice in the summer, and the quantity plotted above (sea ice extent) is somewhat-arbitrarily defined as being the area in which sea ice coverage exceeds 15%. So, for example, a decline in coverage in one particular area from (say) 30% to (say) 20% wouldn’t show up on these graphs. The map below shows the data from which the ‘Sea Ice Extent’ graphs are derived. It is pretty clear that the data present a complex picture.

Colour-coded map showing Arctic sea ice coverage on 23 August 2013. The purple areas are essentially 100% covered, but large areas are only 50%-75% covered, even quite close to the North Pole itself.

This data is derived from the Advanced Microwave Sounding Radiometer 2 (AMSR-2) on board the “Shizuku” (GCOM-W1) satellite launched by the Japanese Space Agency in 2012 to replace an instrument which stopped functioning. The instrument is extraordinary. It measures the extremely weak emissions from the Earth in the microwave part of the electromagnetic spectrum.

As it orbits 700 km above the Earth, a 2 metre diameter mirror captures the microwaves and focusses them onto 6 different detectors sensitive to different microwave frequencies. The mirror rotates every 1.5 seconds allowing the sensors to take data from a swathe of the Earth more than 1000 km across.

The reason I am mentioning all this is to make this simple point: even when one sees relatively simple-to-understand graphs such as those at the start of the page, they are often derived in quite a complex way. Now not everyone needs to know all the details of how every graph we see is derived. But it’s a question which is worth asking every time we see any graph – “Where does that data come from?”

GCSE and A level results: Three steps to make things better

Graph from the BBC showing the increasing GCSE passes. No one thinks this rise is due to increasing educational standards and no one thinks this years fall is due to a fall in standards.

As my own children approach the year in which they will sit GCSE and A level exams, the annual brouhaha  over exam results feels a bit more personal. And my anger over the betrayal of students and the governments abnegation of responsibility in this field grows more intense.

“It wasn’t like this when I were a lad ..”. No really: it wasn’t. Back in the 60’s and 70’s, the results were always the same: for example the top 7.5% (I think that was the number) received an A, the next n% received a B and so on. This approach served to discriminate amongst the candidates. But it didn’t register whether students knew more or less than in previous years.

Then exams were changed in many ways simultaneously. Syllabuses were reduced, continuous assessment introduced, exam boards became wholly-owned by book publishers, and ‘absolute’ marking became the norm. The result was decades of grade inflation and political bickering.

Many educational changes ‘since I were a lad’ have been really positive, and I suspect the general standard of teaching is higher. But I don’t know anyone who thinks that the fact that exam results began to ‘improve’ after 1986  reflects any actual ‘improvement’ in education. In the same way, nobody believes that this year’s small fall in A* to C grades reflects any actual ‘decline’ in educational standards.

It seems that the exam results are telling us nothing about educational standards and this is obviously unsatisfactory. And all this has happened during a period in which schools and exam boards have been subject to more inspections than at anytime in history. I won’t go into the causes of this shameful and ‘almost corrupt’ episode, but the answers are simple,

• Firstly, publishers should not be allowed to own or influence exam boards. ‘Competition’ to produce the easiest exams only drives down standards. Exam boards should set standards and exams, and publishers should produce books that teach the subject in general, not how to pass particular exams in the subject. Ideally there would be only one exam board for each subject.
• Secondly, grade inflation should be eliminated by making A*, A and B grades correspond to fixed fractions of the candidates. Grade A* would mean the top 5% (say), A the next 10% (say) and B the next 20%. However the C mark should be marked on achievement against a standard rather than against other candidates. This allows improvements in education to be reflected in improved results but keeps the significance of higher marks.
• Thirdly, governments then need to stop changing the exam system every few years. A politically-balanced commission should consider changes every 20 years with no ability to change the rules in intervening years. It needs that length of time to measure the effect of any changes which have been made.

I could go on, but I won’t. Education is a precious and important activity and the more kerfuffle there is around this topic the more difficult it is to make the learning magic shimmer.  So I will just wish all teachers and students best wishes for the last weeks of the summer holiday and the start of the new term.