MCQ4 (added 23/09/20) The question provides a histogram for a continuous distribution (bird beak sizes), and asks for the “closest” of five listed values to the interquartile range. As the examination report almost acknowledges (presumably in time for the grading), this cannot be determined from the histogram; three of the listed values may be closest, depending upon the precise distribution. The report suggests one of these values as the “best” estimate, but does not rely upon this suggestion. See the comments below.
MCQ9 Module 2 (added 30/09/20) The question refers to cutting a wedge of cheese to make a “similar” wedge of cheese, but the new wedge is not (mathematically) similar. The exam report states that the word “similar” was intended “in its everyday sense” but noted the confusion, albeit in a weasely, “who woulda thought?” manner. A second answer was marked correct, although only after a fight over the issue.
MCQ20 (added 24/09/20) The notation refers to the forces in the question being asked, and seemingly also in the diagram for the question, but to the magnitudes of these forces in the suggested answers. The examination report doesn’t acknowledge the error.
We’re not really ready to embark upon this post, but it seems best to get it underway ASAP, and have commenters begin making suggestions.
It seems worthwhile to have all the Mathematical Methods exam errors collected in one place: this is to be the place.*
Our plan is to update this post as commenters point out the exam errors, and so slowly (or quickly) we will compile a comprehensive list.
To be as clear as possible, by “error”, we mean a definite mistake, something more directly wrong than pointlessness or poor wording or stupid modelling. The mistake can be intrinsic to the question, or in the solution as indicated in the examination report; examples of the latter could include an insufficient or incomplete solution, or a solution that goes beyond the curriculum. Minor errors are still errors and will be listed.
With each error, we shall also indicate whether the error is (in our opinion) major or minor, and we’ll indicate whether the examination report acknowledges the error, updating as appropriate. Of course there will be judgment calls, and we’re the boss. But, we’ll happily argue the tosses in the comments.
Q3(h), Section B (added 06/10/20)- discussed here. This is the error that convinced us to start this blog. The question concerns a “probability density function”, but with integral unequal to 1. As a consequence, the requested “mean” (part (i)) and “median” (part (ii)) make no definite sense.
There are three natural approaches to defining the “median” for part (ii), leading to three different answers to the requested two decimal places. Initially, the examination report acknowledged the issue, while weasely avoiding direct admission of the fundamental screw-up; answers to the nearest integer were accepted. A subsequent amendment, made over two years later, made the report slightly more honest, although the term “screw-up” still does not appear.
As noted in the comment and update to this post, the “mean” in part (i) is most naturally defined in a manner different to that suggested in the examination report, leading to a different answer. The examination report still fails to acknowledge any issue with part (i).
Q4(c), Section B (added 25/09/20) The solution in the examination report sets up (but doesn’t use) the equation dy/dx = stuff = 0, instead of the correct d/dx(stuff) = 0.
MCQ4 (added 21/09/20) – discussed here. The described function need not satisfy any of the suggested conditions, as discussed here. The underlying issue is the notion of “inflection point”, which was (and is) undefined in the syllabus material. The examination report ignores the issue.
Q7(b) (added 23/09/20)The question asks students to “find p“, where is the probability that a biased coin comes up heads, and where it turns out that . The question is fatally ambiguous, since there is no definitive answer to whether is possible for a “biased coin”.
The examination report answer includes both values of , while also noting “The cancelling out of p was rarely supported; many students incorrectly [sic] assumed that p could not be 0.” The implication, but not the certainty, is that although 0 was intended as a correct answer, students who left out or excluded 0 could receive full marks IF they explicitly “supported” this exclusion.
This is an archetypal example of the examiners stuffing up, refusing to acknowledge their stuff up, and refusing to attempt any proper repair of their stuff up. Entirely unprofessional and utterly disgraceful.
Yesterday, Bach had an op-ed in the official organ of the Liberal Party (paywalled, thank God). Titled We must raise our grades on teacher quality, Bach’s piece was the predictable mix of obvious truth and poisonous nonsense, promoting the testing of “numeracy” and so forth. One line, however, stood out as a beacon of Bachism:
“But, as in any profession, a small number of teachers is not up to the mark.”
“All students were awarded [the] mark for this question.”
Yep, the question is plain stuffed. We think, however, there is more here than the simple wrongness, which is why we’ve made it a WitCH rather than a PoSWW. Happy hunting.
UPDATE (11/05) Steve C’s comment below has inspired an addition:
The third greatest issue with the exam question is that it is wrong: none of the available answers is correct. The second greatest issue is that the wrongness is obvious: if lies in a sector then the natural guess is that will lie in one of three equally spaced sectors of a third the width, so God knows why the alarm bells weren’t ringing. The greatest issue is that VCAA didn’t have the guts or the basic integrity to fess up: not a single word of responsibility or remorse. Assholes.
Those are the elephants stomping through the room but, as commenters as have noted, there is plenty more awfulness in this question:
“Letting” is sloppy, confusing and pointless;
The term “quadrant” is undefined;
The use of “principal” is unnecessary;
“argument” is better thought as the measure of an angle not the angle itself;
Given is a single complex number, “the complete set of values for Arg()” will consist of a single number.
We had plans a week ago (seems like a year ago) for a PoSSW coronavirus post. But, God, there is so much stupid right now. Who could possibly keep up?
Here is a dedicated post for coronavirus-related stupidity. Commenters are welcome to point to and give links to specific idiocies, or simply to vent. We’ll update the post with the hyper-stupids. (So, standard Morrison/Trump/Johnson incompetence doesn’t cut it, but unloading a whole fucking boat of sick people most definitely does.)
PoSWW 2 (26/2) Courtesy of occasional commenter Franz, cardiopraxis.de gives us a graph showing what “uncontrolled exponential spreading of the infection” would look like:
PoSWW 3 (27/2) The Guardian royally fucks up their 96pt bold headline:
A number of prominent public Health Professionals have written an open letter to Australia’s health ministers and (the stunningly appropriately titled) gambling ministers. The letter is written in a predictably calm, professional and diplomatic manner, but we’ll translate: you people who signed off to keep pokies venues open are out of your fucking minds.
This one comes courtesy of Christian, an occasional commenter and professional nitpicker (for which we are very grateful). It is a question from a 2016 Abitur (final year) exam for the German state of Hesse. (We know little of how the Abitur system works, and how this question may fit in. In particular, it is not clear whether the question above is a statewide exam question, or whether it is more localised.)
Christian has translated the question as follows:
A specialty store conducts an ad campaign for a particular smartphone. The daily sales numbers are approximately described by the function g with , where t denotes the time in days counted from the beginning of the campaign, and g(t) is the number of sold smartphones per day. Compute the point in time when the most smartphones (per day) are sold, and determine the approximate number of sold devices on that day.