The Treachery of Images

Harry scowled at a picture of a French girl in a bikini. Fred nudged Harry, man-to-man. “Like that, Harry?” he asked.

“Like what?”

“The girl there.”

“That’s not a girl. That’s a piece of paper.”

“Looks like a girl to me.” Fred Rosewater leered.

“Then you’re easily fooled,” said Harry. It’s done with ink on a piece of paper. That girl isn’t lying there on the counter. She’s thousands of miles away, doesn’t even know we’re alive. If this was a real girl, all I’d have to do for a living would be to stay at home and cut out pictures of big fish.”

                       Kurt Vonnegut, God Bless you, Mr. Rosewater

 

It is fundamental to be able to distinguish appearance from reality. That it is very easy to confuse the two is famously illustrated by Magritte’s The Treachery of Images (La Trahison des Images):

The danger of such confusion is all the greater in mathematics. Mathematical images, graphs and the like, have intuitive appeal, but these images are mere illustrations of deep and easily muddied ideas. The danger of focussing upon the image, with the ideas relegated to the shadows, is a fundamental reason why the current emphasis on calculators and graphical software is so misguided and so insidious.

Which brings us, once again, to Mathematical Methods. Question 5 on Section Two of the second 2015 Methods exam is concerned with the function V:[0,5]\rightarrow\Bbb R, where

\phantom{\quad}  V(t) = de^{\frac{t}3} + (10-d)e^{\frac{-2t}3}\,.

Here, d \in (0,10) is a constant, with d=2 initially; students are asked to find the minimum (which occurs at t = \log_e8), and to graph V. All this is par for the course: a reasonable calculus problem thoroughly trivialised by CAS calculators. Predictably, things get worse.

In part (c)(i) of the problem students are asked to find “the set of possible values of d” for which the minimum of V occurs at t=0. (Part (c)(ii) similarly, and thus boringly and pointlessly, asks for which d the minimum occurs at t=5). Arguably, the set of possible values of d is (0,10), which of course is not what was intended; the qualification “possible” is just annoying verbiage, in which the examiners excel.

So, on to considering what the students were expected to have done for (c)(ii), a 2-mark question, equating to three minutes. The Examiners’ Report pointedly remarks that “[a]dequate working must be shown for questions worth more than one mark.” What, then, constituted “adequate working” for 5(c)(i)? The Examiners’ solution consists of first setting V'(0)=0 and solving to give d=20/3, and then … well, nothing. Without further comment, the examiners magically conclude that the answer to (c)(i) is 20/3 \leqslant d< 10.

Only in the Carrollian world of Methods could the examiners’ doodles be regarded as a summary of or a signpost to any adequate solution. In truth, the examiners have offered no more than a mathematical invocation, barely relevant to the question at hand: why should V having a stationary point at t=0 for d=20/3 have any any bearing on V for other values of d? The reader is invited to attempt a proper and substantially complete solution, and to measure how long it takes. Best of luck completing it within three minutes, and feel free to indicate how you went in the comments.

It is evident that the vast majority of students couldn’t make heads or tails of the question, which says more for them than the examiners. Apparently about half the students solved V'(0)=0 and included d = 20/3 in some form in their answer, earning them one mark. Very few students got further; 4% of students received full marks on the question (and similarly on (c)(ii)).

What did the examiners actually hope for? It is pretty clear that what students were expected to do, and the most that students could conceivably do in the allotted time, was: solve V'(0)=0 (i.e. press SOLVE on the machine); then, look at the graphs (on the machine) for two or three values of d; then, simply presume that the graphs of V for all d are sufficiently predictable to “conclude” that 20/3 is the largest value of d for which the (unique) turning point of V lies in [0,5]. If it is not immediately obvious that any such approach is mathematical nonsense, the reader is invited to answer (c)(i) for the function W:[0,5]\rightarrow\Bbb R where W(t) = (6-d)t^2 + (d-2)t.

Once upon a time, Victorian Year 12 students were taught mathematics, were taught to prove things. Now, they’re taught to push buttons and to gaze admiringly at pictures of big fish.

The “Marriage Theorem” Theorem

The Marriage Theorem is a beautiful piece of mathematics, proved in the 1930s by mathematician Philip Hall. Suppose we have a number of men and the same number of women. Each man is happy to marry some (but perhaps not all) of the women, and similarly for each woman. The question is, can we pair up all the men and women so that everyone is happily married?

Obviously this will be impossible if too many people are too fussy. We’ll definitely require, for example, each woman to be happy to marry at least one man. Similarly, if we take any pair of women then there’s no hope if those two women are both just keen on the one and same man. More generally, we can take any collection W the women, and then we can consider the collection M of men who are acceptable to at least one of those women. The marriage condition states that, no matter the collection W, the corresponding collection M is at least as large as W.

If the marriage condition is not satisfied then there’s definitely no hope of happily marrying everyone off. (If the condition fails for some W then there simply aren’t enough acceptable men for all the women in W.) The Marriage Theorem is the surprising result that the marriage condition is all we need to check; if the marriage condition is satisfied then everyone can be happily married.

That’s all well and good. It’s a beautiful theorem, and you can check out a very nice proof at (no pun intended) cut-the-knot. This, however, is a blog about mathematical crap. So, where’s the crap? For that, we head off to Sydney’s University of New South Wales.

It appears that a lecturer at UNSW who has been teaching the Marriage Theorem has requested that students not refer to the theorem by that name, because of the “homophobic implications”; use of the term in student work was apparently marked as “offensive”. How do we know this? Because one of the affected students went on Sky News to tell the story.

And there’s your crap.

But, at least we have a new theorem:

The “Marriage Theorem” Theorem

a) Any mathematician who whines to her students about the title “Marriage Theorem” is a trouble-making clown with way too much time on her hands.

b) Any student who whines about the mathematician in (a) to a poisonously unprincipled pseudonews network is a troublemaking clown with way too much time on his hands.

Proofs: Trivial.

Going off at a Tangent

So Plimpton 322, the inscrutable Babylonian superstar, has suddenly become scrutable. After a century of mathematics historians puzzling over 322’s strange list of Pythagorean triples, two UNSW mathematics have reportedly solved the mystery. Daniel Mansfield and Norman Wildberger have determined that this 3,800-ish year old clay tablet is most definitely a trigonometry table. Not only that, the media have reported that this amazing table is “more accurate than any today“, and “will make studying mathematics easier“.

Yeah, right.

Evelyn Lamb has provided a refreshingly sober view of all this drunken bravado. For a deeper history and consideration, read Eleanor Robson.

Babylonian mathematics is truly astonishing, containing some great insights. It would be no surprise if (but it is by no means guaranteed that) Plimpton 322 contains.great mathematics. What is definitely not great is to have a university media team encourage lazy journalists to overhype what is probably interesting research to the point of meaninglessness.

The Marriage Equality Theorem

Theorem: Let V be the set of valid arguments against marriage equality. Then is empty.

Proof: Let P be a valid argument. Then, by now, someone would have argued P. This has not occurred. (Proof: by exhaustion.) By contradiction, it follows that P does not exist, and thus V is empty. QED.

An alternative, direct proof of the theorem was provided by the California Supreme Court; their proof applied the definition of equality.

Consideration of the many straight-forward corollaries of this theorem are left to the reader.

Three Apples + Two Oranges = Infinite Nonsense

The key findings of Australia’s 2016 National Drug Strategy Household Survey were released earlier this year, and they made for sobering reading. The NDSHS reported that over 15% of Australians had used illicit drugs in the previous year, including such drugs as cannabis, ice and heroin. Shocking, right?

Wrong. Of course.

We’re being silly in a way that the NDSHS reporting was not. Yes, the NDSHS reported that 15% had used illicit drugs at least once (including the possibility of exactly once) in the previous year, but NDSHS also emphasised the composition of that 15%. By far the most commonly used drug was cannabis, at about 10% of the population. Ice use was around 1%, and heroin didn’t register in the summary.

Illicit drug use is a serious problem, and a problem exacerbated by idiotic drug laws. Nothing can be learned, however, and nothing can be solved if one focuses upon a meaningless 15% multicategory. Whatever the specific threats or the reasonableness of concerns over the broad use of cannabis, such concerns pale in comparison to the problems of ice and heroin. The NDSHS makes no such categorical mistake. Unfortunately, there are plenty of clowns who do.

Last week, the Federal Ministers for Social Services and Human Services announced the location of a drug testing trial for job seekers who receive federal benefits. The ironically named Christian Porter and the perfectly named Alan Tudge announced that receipients would be tested “for illicit substances including ice (methamphetamine), ecstasy (MDMA) and marijuana (THC) … People who test positive to drug tests will continue to receive their welfare payment but 80 per cent of their payment will only be accessible through Income Management.” The plan is deliberately nasty and monumentally stupid, and it has been widely reported as such. For all the critical reporting, however, we could find no instance of the media noting the categorical lunacy of effectively equating the use of ice and ecstasy and THC.

Still, one should be fair to Porter and Tudge. They are undeniably dickheads, but Porter and Tudge are hardly exceptional. They are members of a very large group of thuggish, victim-blaming politicians, which includes Malcolm Turnbull, and Peter Dutton, and Adolf Hitler.

It is also notable that this kind of multicategory crap is only practised by social conservatives. It’s not like a nationwide survey on sexual harrassment and sexual assault in universities would ever couch the results in broadly defined categories in such a clouded and deceptive manner. Nope, not a chance.

NAPLAN’s Numerological Numeracy

This year Australia celebrates ten years of NAPLAN testing, and Australians can ponder the results. Numerous media outlets have reported “a 2.55% increase in numeracy” over the ten years. This is accompanied by a 400% increase in the unintended irony of Australian education journalism.

What is the origin of that 2.55% and precisely what does it mean to have “an increase in numeracy” by that amount? Yes, yes, it clearly means “bugger all”, but bugger all of what? It is a safe bet that no one reporting the percentage has a clue, and it is not easy to determine.

The media appear to have taken the percentage from a media release from Simon Birmingham, the Federal Education and Training Minister. (Birmingham, it should be noted, is one of the better ministers in the loathsome Liberal government; he is merely hopeless rather than malevolent.) Attempting to decipher that 2.55%, it seems to refer to the “% average change in NAPLAN mean scale score [from 2008 to 2017], average for domains across year levels”. Whatever that means.

ACARA, the administrators of NAPLAN, issued their own media release on the 2017 NAPLAN results. This release does not quote any percentages but indicates that the “2107 summary information” can be found at the the NAPLAN reports page. Two weeks after ACARA’s media release, no such information is contained on or linked on that page, nor on the page titled NAPLAN 2017 summary results. Both pages link to a glossary, to explain “mean scale score”, which in turn explains nothing. The 2016 NAPLAN National Report contains the expression 207 times, without once even pretending to explain what it means. The 609-page Technical Report from 2015 (the latest available on ACARA’s website) appears to contain the explanation, though the precise expression is never used and nothing remotely resembling a user-friendly summary is included.

To put it very briefly, each student’s submitted test is given a “scaled score”. One purpose of this is to be able to compare tests and test scores from different years. The statistical process is massively complicated and in particular it includes a weighting for the “difficulty” of each test question. There is plenty that could be queried here, particularly given ACARA’s peculiar habit of including test questions that are so difficult they can’t be answered. But, for now, we’ll accept those scaled scores as a thing. Then, for example, the national average for 2008 Year 3 numeracy scaled scores was 396.9. This increased to 402.0 in 2016, amounting to a percentage increase of 1.29%. The average percentage increases from 2008 to 2017 can then be further averaged over the four year levels, and (we think) this results in that magical 2.55%.

It is anybody’s guess whether that “2.55% increase in numeracy” corresponds to anything real, but the reporting of the figure is simply hilarious. Numeracy, to the very little extent it means anything, refers to the ability to apply mathematics effectively in the real world. To then report on numeracy in such a manner, with a who-the hell-cares free-floating percentage is beyond ironic; it’s perfect.

But of course the stenographic reportage is just a side issue. The main point is that there is no evidence that ten years of NAPLAN testing, and ten years of shoving numeracy down teachers’ and students’ throats, has made one iota of difference.

Malcolm the Mathematician

Australia’s Prime Minister tends to be pretty pleased with himself, and plenty of other people seem to think of Malcolm Turnbull as the smartest guy in the room. Perhaps he sometimes he is.* Malcolm didn’t appear so smart, however, when presenting Australia’s proposal to require the tech giants to decrypt their customers’ encrypted messages. When ZDnet reporter Asha McLean suggested that “the laws of mathematics [might] trump the laws of Australia”, Malcolm was unfazed:

The laws of Australia prevail in Australia, I can assure you of that. The laws of mathematics are very commendable but the only law that applies in Australia is the law of Australia.

And yes, the Government’s plan (for want of a better word) is as clueless as Malcolm makes it sound.

We already knew that Malcolm was a scientific clown, an economic illiterate, a coward, a Luddite, an Orwellian thug and a moral midget. So, maybe it shouldn’t be a great surprise when Malcolm also turns out to be an anti-mathematical git.

* If the other people in the room are Peter Dutton and Barnaby Joyce.

The Mysterious Wisdom of the East

According to The Australian newspaper (paywalled), a bunch of “education and policy experts” have headed to China in an attempt to address Australia’s educational woes:

Frustrated by stagnating maths and STEM standards, [they] are travelling to China for lessons on how to boost maths and science in local classrooms. 

Gee, I wonder what they might learn. What secret path to mathematical facility could those inscrutable Chinese possess? A wonderful new app, maybe. Or perhaps Chinese schools flip their classrooms in some really special way. 

But, whatever their secret, it may not help us to learn it. The worth of “importing other countries’ teachings practices” is apparently questionable, “given that education is woven within the cultural fabric of nations.”

There’s plenty woven within (?) the cultural fabric of Australia, but whether one should refer to it as education is open to debate.

NAPLAN’s Mathematical Nonsense, and What it Means for Rural Peru

The following question appeared on Australia’s Year 9 NAPLAN Numeracy Test in 2009:

y = 2x – 1

y = 3x + 2

Which value of x satisfies both of these equations?

It is a multiple choice question, but unfortunately “The question is completely stuffed” is not one of the available answers.

Of course the fundamental issue with simultaneous equations is the simultaneity. Both equations and both variables must be considered as a whole, it simply making no sense to talk about solutions for x without reference to y. Unless y = -7 in the above equations, and there is no reason to assume that, then no value of x satisfies both equations. The NAPLAN question is way beyond bad.

It is always worthwhile pointing out NAPLAN nonsense, as we’ve done before and will continue to do in the future. But what does this have to do with rural Peru?

In a recent post we pointed out an appalling question from a nationwide mathematics exam in New Zealand. We flippantly remarked that one might expect such nonsense in rural Peru but not in a wealthy Western country such as New Zealand. We were then gently slapped in the comments for the Peruvian references: Josh queried whether we knew anything of Peru’s educational system; and, Dennis questioned the purpose of bringing up Peru, since Australia’s NAPLAN demonstrates a “level of stupidity” for all the World to see. These are valid points.

It would have been prudent to have found out a little about Peru before posting, but we seem to be safe. Peru’s economy has been growing rapidly but is not nearly as strong as New Zealand’s or Australia’s. Peruvian school education is weak, and Peru seems to have no universities comparable to the very good universities in New Zealand and Australia. Life and learning in rural Peru appears to be pretty tough.

None of this is surprising, and none of it particularly matters. Our blog post referred to “rural Peru or wherever”. The point was that we can expect poorer education systems to throw up nonsense now and then, or even typically; in particular, lacking ready access to good and unharried mathematicians, it is unsurprising if exams and such are mathematically poor and error-prone.

But what could possibly be New Zealand’s excuse for that idiotic question? Even if the maths ed crowd didn’t know what they were doing, there is simply no way that a competent mathematician would have permitted that question to remain as is, and there are plenty of excellent mathematicians in New Zealand. How did a national exam in New Zealand fail to be properly vetted? Where were the mathematicians?

Which brings us to Australia and to NAPLAN. How could the ridiculous problem at the top of this post, or the question discussed here, make it into a nationwide test? Once again: where were the mathematicians?

One more point. When giving NAPLAN a thoroughly deserved whack, Dennis was not referring to blatantly ill-formed problems of the type above, but rather to a systemic and much more worrying issue. Dennis noted that NAPLAN doesn’t offer a mathematics test or an arithmetic test, but rather a numeracy test. Numeracy is pedagogical garbage and in the true spirit of numeracy, NAPLAN’s tests include no meaningful evaluation of arithmetic or algebraic skills. And, since we’re doing the Peru thing, it seems worth noting that numeracy is undoubtedly a first world disease. It is difficult to imagine a poorer country, one which must weigh every educational dollar and every educational hour, spending much time on numeracy bullshit.

Finally, a general note about this blog. It would be simple to write amusing little posts about this or that bit of nonsense in, um, rural Peru or wherever. That, however, is not the purpose of this blog. We have no intention of making easy fun of people or institutions honestly struggling in difficult circumstances; that includes the vast majority of Australian teachers, who have to tolerate and attempt to make sense of all manner of nonsense flung at them from on high. Our purpose is to point out the specific idiocies of arrogant, well-funded educational authorities that have no excuse for screwing up in the manner in which they so often do.

Obtuse Triangles

Whatever the merits of undertaking a line by line critique of the Australian Curriculum, it would take a long time, it would be boring and it would probably overshadow the large, systemic problems. (Also, no one in power would take any notice, though that has never really slowed us down.) Still, the details should not be ignored, and we’ll consider here one of the gems of Homer Simpson cluelessness.

In 2010, Burkard Polster and I wrote an Age newspaper column about a draft of the Australian Curriculum. We focused on one line of the draft, an “elaboration” of Pythagoras’s Theorem:

recognising that right-angled triangle calculations may generate results that can be integral, fractional or irrational numbers known as surds

Though much can be said about this line, the most important thing to say is that it is wrong. Seven years later, the line is still in the Australian Curriculum, essentially unaltered, and it is still wrong.

OK, perhaps the line isn’t wrong. Depending upon one’s reading, it could instead be meaningless. Or trivial. But that’s it: wrong and meaningless and trivial are the only options.

The weird grammar and punctuation is standard for the Australian Curriculum. It takes a special lack of effort, however, to produce phrases such as “right-angled triangle calculations” and “generate results”. Any student who offered up such vague nonsense in an essay would know to expect big red strokes and a lousy grade. Still, we can take a guess at the intended meaning.

Pythagoras’s Theorem can naturally be introduced with 3-4-5 triangles and the like, with integer sidelengths. How does one then obtain irrational numbers? Well, “triangle calculations” on the triangle below can definitely “generate” irrational “results”:

Yeah, yeah, \pi is not a “surd”.  But of course we can replace each \pi by √7 or 1/7 or whatever, and get sidelengths of any type we want. These are hardly “triangle calculations”, however, and it makes the elaboration utterly trivial: fractions “generate” fractions, and irrationals “generate” irrationals. Well, um, wow.

We assume that the point of the elaboration is that if two sides of a right-angled triangle are integral then the third side “generated” need not be. So, the Curriculum writers presumably had in mind 1-1-√2 triangles and the like, where integers unavoidably lead us into the world of irrationals. Fair enough. But how, then, can we similarly obtain the promised (non-integral) fractional sidelengths? The answer is that we cannot.

It is of course notable that two sides of a right-angled triangle can be integral with the third side irrational. It is also notable, however, that two integral sides cannot result in the third side being a non-integral fraction. This is not difficult to prove, and makes a nice little exercise; the reader is invited to give a proof in the comments. The reader may also wish to forward their proof to ACARA, the producers of the Australian Curriculum.

How does such nonsense make it into a national curriculum? How does it then remain there, effectively unaltered, for seven years? True, our 2010 column wasn’t on the front of the New York Times. But still, in seven years did no one at ACARA ever get word of our criticism? Did no one else ever question the elaboration to anyone at ACARA?

But perhaps ACARA did become aware of our or others’ criticism, reread the elaboration, and decided “Yep, it’s just what we want”. It’s a depressing thought, but this seems as likely an explanation as any.