The Year(s) of Replication #las17ed L@S 2017

Posted: April 22, 2017 | Author: | Filed under: Education, Opinion | Tags: , , , , , , , , , , | 6 Comments

I was at Koli Calling in 2016 and a paper was presented (“Replication in Computing Education Research: Researcher Attitudes and Experiences”) regarding the issue of replicating previous studies. Why replicate previous work? Because we have a larger number of known issues that have emerged in psychology and the medical sciences, where important work has not been able to be replicated. Perhaps the initial analysis was underpowered, perhaps the researchers had terrible bad luck in their sample, and perhaps there were… other things going on. Whatever the reason, we depend upon replication as a validation tool and being unable to replicate work puts up a red flag.

ReplyHazy

After the paper, I had follow-up discussions with Andrew Petersen, from U Toronto, and we talked about the many problems. If we do choose to replicate studies, which ones do we choose? How do we get the replication result disseminated, given that it’s fundamentally not novel work? When do we stop replicating? What the heck do we do if we invalidate an entire area of knowledge? Andrew suggested a “year of replication” as a starting point but it’s a really big job: how do we start a year of replication studies or commit to doing this as a community?

This issue was raised again at Learning@Scale 2017 by Justin Reich, from MIT, among others. One of the ideas that we discussed as part of that session was that we could start allocating space at the key conferences in the field for replication studies. The final talk as part of L@S was “Learning about Learning at Scale: Methodological Challenges and Recommendations”, which discussed general problems that span many studies and then made recommendations as to how we could make our studies better and reduce the risk of failing future replication. Justin followed up with comments (which he described as a rant but he’s being harsh) about leaving room to make it easier to replicate and being open to this kind of examination of our work: we’re now thinking about making our current studies easier to replicate and better from the outset, but how can we go back and verify all of the older work effectively?

I love the idea of setting aside a few slots in every conference for replication studies. The next challenge is picking the studies but, given each conference has an organising committee, a central theme, and reviewers, perhaps each conference could suggest a set and then the community identify which ones they’re going to have a look at. We want to minimise unnecessary duplication, after all, so some tracking is probably a good idea.

There are several problems to deal with: some political, some scheduling, some scientific, some are just related to how hard it is to read old data formats. None of them are necessarily insurmountable but we have to be professional, transparent and fair in how we manage them. If we’re doing replication studies to improve confidence in the underlying knowledge of the field, we don’t want to damage the community in doing it.

Let me put out a gentle call to action, perhaps for next year, perhaps for the year after. If you’re involved with a conference, why not consider allocating a few slots to replication studies for the key studies in your area, if they haven’t already been replicated? Even the opportunity to have a community discussion about which studies have been effectively replicated will help identify what we can accept as well as showing us what we could fix.

Does your conference have room for a single track, keynote-level session, to devote some time to replication? I’ll propose a Twitter hashtag of #replicationtrack to discuss this and, hey, if we get a single session in one conference out of this, it’s more than we had.

SIGCSE Day 3, “What We Say, What They Do”, Saturday, 9-10:15am, (#SIGCSE2014)

Posted: March 9, 2014 | Author: | Filed under: Education | Tags: , , , , , , , , , , , , , , , , , | 3 Comments

The first paper was “Metaphors we teach by” presented by Ben Shapiro from Tufts. What are the type of metaphors that CS1 instructors use and what are the wrinkles in these metaphors. What do we mean by metaphors? Ben’s talking about conceptual metaphors, linguistic devices to allow us to understand one idea in terms o another idea that we already know. Example: love is a journey – twists and turns, no guaranteed good ending, The structure of a metaphor is that you have a thing we’re trying to explain (the target) in terms of something we already know (the source).  Conceptual metaphors are explanatory devices to assist us in understanding new things.

Metaphors are widely used in teaching in CS, pointers, stacks and loops – all metaphorical aspects of computer science, but that’s not the focus of this study. How do people teach with metaphor? The authors couldn’t find any studies on general metaphor use in CS and its implication on student learning. An example from a birds-of-a-feather session held at this conference, a variable is like a box. A box can hold many different things but it holds things. (This has been the subject of a specific study.) Ben also introduced the “Too much milk” metaphor. This metaphor is laid out as follows. Jane comes home from work, goes to get milk from the fridge but her roommate has already drunk it (bad roommate!). Jane goes out to get more milk. While she’s out, her roommate comes back with milk, then Jane comes back with milk. Now they have too much milk! This could be used to explain race conditions in CS. Another example is the use of bus lockers mapping to virtual memory.
Ben returned to boxes again? One of the problems is that boxes can hold many things but a variable can only hold one thing – which appears to be a confusing point for learners who knew how boxes work. Is this a common problem? Metaphors have some benefits but come with this kind of baggage? Metaphors are partial mappings – they don’t match every aspect of the target to the source. (If it was a complete mapping they’d be the same thing.)
The research questions that the group considered were:
  • What metaphors do CS1 instructors use for teaching?
  • What are the trying to explain?
  • What are the sources that they use?
Learners don’t know where the mappings start and stop – where do the metaphors break down for students? What mistakes do they make because of these misunderstandings? Why does this matter? We all have knowledge on how to explain but we don’t have good published collections of the kind of metaphors that we use to teach CS, which would be handy for new teachers. We could study these and work out which are more effective. What are the most enduring and universal metaphors?
The study was interview-based, interviewing Uni-level CS1 instructors, ended up with 10 people, with an average of 13 years of teaching.  The interview questions given to these instructors were (paraphrased):
  • Levels taught and number of years
  • Tell me about a metahpor
  • Target to source mapping
  • Common questions students have
  • Where the metaphor breaks down
  • How to handle the breakdown in teaching.
Ben then presented the results. (We had a brief discussion of similes versus metaphors but I’ll leave that to you.) An instructor discussed using the simile of a portkey from Harry Potter to explain return statements in functions, because students had trouble with return existing immediately. The group of 10 people provided 18 different CS Concepts (Targets) and 19 Metaphorical Explanations (Sources).
What’s the target for “Card Catalogs”? Memory addressing and pointers. The results were interesting – there’s a wide range of ways to explain things! (The paper contains a table of a number of targets and sources.)
Out of date cultural references were identified as a problem and you have to be aware of the students’ cultural context. (Card desk and phone booths are nowhere near as widely used as they used to be.) Where do students make inferences beyond the metaphor? None of the 10 participants could give a single example of this happening! (This is surprising – Ben called it weird.) Two hypotheses – our metaphors are special and don’t get overextended (very unlikely) OR CS1 instructors poorly understand student thinking (more likely).
The following experimental studies may shed some light on this:
  • Which metaphors work better?
  • Cognitive clinical internviews, exploring how students think with metaphors and where incorrect inferences are drawn.
There was also a brief explanation of PCK (teachers’ pedagogical content knowledge) but I don’t have enough knowledge to fully flesh this out. Ben, if you’re reading this, feel free to add a beautifully explanatory comment. 🙂
The next walk was “‘Explain in Plain English’ Questions Revisited: Data Structures Problems” presented by Sue Fitzgerald and Laurie. This session opened with a poll to find out what the participants wanted and we all wanted to find out how to get students to use plain English. An Explain in Plain English  (EiPE) question asks you to describe what a chunk of code does, but not in a line by line discussion. A student’s ability to explain what a chink of code does correlates with a student’s ability to write and read code. The study wanted to investigate if this was just a novice phenomenon or if this advanced during the years and expertise. This study looked at 120 undergraduates in a CS2 course in data structures and algorithms using C++, with much more difficult questions than in earlier studies: linked lists, recursive calls and so on.
The students were given two questions in an exam with some preamble to describe the underlying class structure with a short example and a diagram. The students then had to look at a piece of code and determine what would happen in order to answer in the question as a plain English response. (There’s always a problem where you throw to an interactive response system where the question isn’t repeated, perhaps we need two screens.)
The SOLO taxonomy was used to analyse the problems (more Neo-Piagetian goodness!). Four of the SOLO categories were used: relational (summarises the code), multistructural (line by line explanation of the code) , unistructural (only describes one portion rather than the whole idea), and pre structural (misses it completely, gibberish). I was interested to see the examples presented, with pointers and mutual function calling, because it quickly became apparent that the room I was in (which had a lot of CS people in it) were having to think relatively hard about the answer to the second example. One of the things about working memory is that it’s not very deep and none of us were quite ready to work in a session 🙂 but a lot of good discussion ensued. The students would have had ready access to the preamble code but I do wonder how much obfuscation is really required here. The speaker made a parenthetical comment that experts usually doodle but where was our pen and paper! (As someone else said, reinforcing the point that we didn’t come prepared to work, nobody told us we had to bring paper. 🙂 ) We then got to classify a student response that was quite “student-y”. (A question came up as to whether an answer can be relational if it’s wrong – the opinion appears to be that a concise, complete and incorrect answer could be considered relational. A point for later discussion.) The answer we saw was multistructural because it was a line-by-line answer – it wasn’t clear, concise and abstract. We then saw another response that was much more terse but far less accurate. THe group tossed up between unistructural and pre structural. (The group couldn’t see the original code or the question, so this uncertainty make sense. Again, a problem with trying to have an engaging on-line response system and a presentation on the same screen. The presenters did a great job of trying to make it work but it’s not ideal.)
What about correlations? For the first question asked, students who gave relational and multistructural answers generally passed, with a 58% grade. Those who answered at the uni or pre level generally failed with an average grade of 38%. In the second test question, the relational and multi group generally passed with a grade of 61.2%, the uni and pre group generally failed with an achieved grade of 42%.
So these correlations hold for no-novice programmers. A mix of explaining, writing and reading code is an effective way to develop good programming skills and EiPE questions give students good practice in the valuable skills of explaining code. Instructors can overestimate how well students understand presented code – asking them to explain it back is very useful for student self-assessment. The authors’ speculation is that explaining code to peers is probably part of the success of peer instruction and pair programming.
The final talk was “A Formative Study of Influences on Student Testing Behaviours” presented by Kevin Buffardi, from VT. In their introductory CS1 and CS2 courses they use Test-Driven Development (TDD) – code a little, test a little, for incremental development. It’s popular in industry, so students come out with relevant experience, but some previous studies have found improvement in student work when they closely adhered to TDD philosophy. BUT a lot of students didn’t follow it at all! So the authors were looking for ways to encourage students to follow this, especially when they were on their own and programming by themselves. Because it’s a process, you can tell what happened by looking at the final program but they use WebCAT and so can track the developmental stages of the program as students submit their work for partial grading. These snapshots provide clear views of what the students are doing over time. (I really have to look at what we could do with WebCAT. Our existing automarker is getting a bit creaky.) Students also received hints back when they submitted their work, general and instructor level.
The first time students achieved something with any type of testing, they would get a “Good Start” feedback and be entitled to a free hint. If you kept up with your testing, you would ‘buy’ more hints. If your test coverage was good, you got more hints. If your coverage was poor, you got general feedback. (Prior to this, WebCAT only gave 3 hints. Now there are no free hints but you can buy an unlimited number.) This is an adaptive feedback mechanism, to encourage testing with hints as incentives. The study compared reinforcement treatments:
  • Constant – even time a goal achieve, you got a hint (Consistently rewards target behaviour)
  • Delayed – Hints when earned, at most one hint per hour (less inceptive for hammering the system)
  • Random – 50% chance of hints when goal is met. (Should reduce dependency on extrinsic behaviours)
Should you show them the goal or not? This was an additional factor – the goals were either visual (concrete goal) or obscured (suggest improvement without specified target). These were a paired treatment.
What was the impact? There were no differences in the number of lines written, but the visual goal lead to students getting better test coverage than obscured goal. There didn’t appear to be a long term effect but there is an upcoming ITiCSE talk that will discuss this further. There were some changes from one submission to another but this wasn’t covered in detail.
The authors held formative group interviews where the students explained their development process and interaction with WebCAT. They said that they valued several types of evaluation, they paid attention to RED progress bars (visualisation and dash boarding – I’d argue that is is more about awareness than motivation), and noticed when they earned a hint but didn’t get it. The students drew their individual developmental process as a diagram and, while everyone had a unique approach, but there were two general approaches. Test last approach showed up: write a solution, submit a solution to WebCAT, take a break, do some testing, then submit to WebCAT again. Periodic testing approach was the other pattern seen, where they wrote solutions, WebCAT, write tests, submit to WebCAT, then revise solution and tests, and iterate.
Going forward, the automated evaluation became part of their development strategy. There were conflicting interests: the correctness reports from WebCAT were actually reducing the need to write their own tests because they were getting an indication of how well it was working. This is an important point for me, because from the examples I saw, I really couldn’t see what I would call test-driven development, especially for test last, so the framework is not encouraging the right behaviour. Kevin handled my question on this well, because it’s a complicated issue, and I’m really looking forward to seeing the ITiCSE paper follow-up! Behavioural change is difficult and, as Kevin rightly noted, it’s optimistic to think that we can achieve it in the short term.
Everyone wants to get students doing the right thing but it’s a very complicated issue. Much food for thought and a great session!

When the Stakes are High, the Tests Had Better Be Up to It.

Posted: July 2, 2012 | Author: | Filed under: Education, Opinion | Tags: , , , , , , , , , , , , , , , , , , , , , | Leave a comment

(This is on the stronger opinion side but, in the case of standardised testing as it is currently practised, this will be a polarising issue. Please feel free to read the next article and not this one.)

If you make a mistake, please erase everything from the worksheet, and then leave the room, as you have just wasted 12 years of education.

A friend on FB (thanks, Julie!) linked me to an article in the Washington Post that some of you may have seen. The article is called “The Complete List of Problems with High-Stakes Standardised Tests” by Marion Brady, in the words of the article. a “teacher, administrator, curriculum designer and author”. (That’s attribution, not scare quotes.)

Brady provides a (rather long but highly interesting) list of problems with the now very widespread standardised testing regime that is an integral part of student assessment in some countries. Here. Brady focuses on the US but there is little doubt that the same problems would exist in other areas. From my readings and discussions with US teachers, he is discussing issues that are well-known problems in the area but they are slightly intimidating when presented as a block.

So many problems are covered here, from an incorrect focus on simplistic repetition of knowledge because it’s easier to assess, to the way that it encourages extrinsic motivations (bribery or punishment in the simplest form), to the focus on test providers as the stewards and guides of knowledge rather than the teachers. There are some key problems, and phrases, that I found most disturbing, and I quote some of them here:

[Teachers oppose the tests because they]

“unfairly advantage those who can afford test prep; hide problems created by margin-of-error computations in scoring; penalize test-takers who think in non-standard ways”

“wrongly assume that what the young will need to know in the future is already known; emphasize minimum achievement to the neglect of maximum performance; create unreasonable pressures to cheat.”

“are open to massive scoring errors with life-changing consequences”

“because they provide minimal to no useful feedback”

This is completely at odds with what we would consider to be reasonable education practice in any other area. If I had comments from students that identified that I was practising 10% of this, I would be having a most interesting discussion with my Head of School concerning what I was doing – and a carpeting would be completely fair! This isn’t how we should teach and we know it.

I spoke yesterday about an assault on critical thinking as being an assault on our civilisation, short-sightedly stabbing away at helping people to think as if it will really achieve what (those trying to undermine critical thinking) actually wanted. I don’t think that anyone can actually permanently stop information spreading, when that information can be observed in the natural world, but short-sightedness, malign manipulation of the truth and ignorance can certainly prevent individuals from gaining access to information – especially if we are peddling the lie that “everything which needs to be discovered is already known.”

We can, we have and we probably (I hope) always will work around these obstacles in information, these dark ages as I referred to them yesterday, but at what cost of the great minds who cannot be applied to important problems because they were born to poor families, in the ‘wrong’ state, in a district with no budget for schools, or had to compete against a system that never encouraged them to actually think?

The child who would have developed free safe power, starship drives, applicable zero-inflation stable economic models, or the “cure for cancer” may be sitting at the back of a poorly maintained, un-airconditioned, classroom somewhere, doodling away, and slowly drifting from us. When he or she encounters the standardised test, unprepared, untrained, and tries to answer it to the extent of his or her prodigious intellect, what will happen? Are you sufficiently happy with the system that you think that this child will receive a fair hearing?

We know that students learn from us, in every way. If we teach something in one way but we reward them for doing something else in a test, is it any surprise that they learn for the test and come to distrust what we talk about outside of these tests? I loathe the question “will this be in the exam” as much as the next teacher but, of course, if that is how we have prioritised learning and rewarded the student, then they would be foolish not to ask this question. If the standardised test is the one that decides your future, then, without doubt, this is the one that you must set as your goal, whether student, teacher, district or state!

Of course, it is the future of the child that is most threatened by all of this, as well as the future of the teaching profession. Poor results on a standardised test for a student may mean significantly reduced opportunity, and reduced opportunity, unless your redemptive mechanisms are first class, means limited pathways into the future. The most insidious thread through all of this is the idea that a standardised test can be easily manipulated through a strategy of learning what the answer should be, to a test question, rather than what it is, within the body of knowledge. We now combine the disadvantaged student having their future restricted, competing against the privileged student who has been heavily channeled into a mode that allows them to artificially excel, with no guarantee that they have the requisite aptitude to enjoy or take advantage of the increased opportunities. This means that both groups are equally in trouble, as far as realising their ambitions, because one cannot even see the opportunity while the other may have no real means for transforming opportunity into achievement.

The desire to control the world, to change the perception of inconvenient facts, to avoid hard questions, to never be challenged – all of these desires appear to be on the rise. This is the desire to make the world bend to our will, the real world’s actual composition and nature apparently not mattering much. It always helps me to remember that Cnut stood in the waves and commanded them not to come in order to prove that he could not control the waves – many people think that Cnut was defeated in his arrogance, when he was attempting to demonstrate his mortality and humility, in the face of his courtiers telling him that he had power above that of mortal men.

How unsurprising that so many people misrepresent this.