Gas station without pumps

2016 April 10

Transfer of learning

Filed under: Circuits course — gasstationwithoutpumps @ 09:58
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In a recent e-mail list discussion, being a math major was justified by the transferability of problem-solving skills from one domain (math) to others (banking, sales, and other jobs).  This justification for studying math is a popular one with mathematicians and math teachers.  One of the primary justifications for requiring geometry, for example, is that it teaches students how to prove things rigorously.​  The same case for transferable problem solving can be (and has been) made, perhaps even more strongly, for computer science and for engineering fields that do a lot of design work.
I was a math major (through and MS) and I got my PhD in computer science, and I certainly believed that the constant practice at problem solving made me better at solving certain classes of problems—ones with clear rules, not social problems or biological ones.
Education researchers have tried to measure this transfer effect, but so far have come up empty, with almost no indication of transfer except between very, very close domains.  I don’t know whether the problem is with the measurement techniques that the education researchers use, or whether (as they claim) transferability is mainly an illusion.  Perhaps it is just because I’m good at problem solving of a certain sort that I went into math and computer science, and that the learning I did there had no effect on my problem-solving skill, other than tuning it to particular domains (that is, perhaps the transferable skill was innate, at the learning reduced transfer, by focusing the skills in a specialized domain).
Two of the popular memes of education researchers, “transferability is an illusion” and “the growth mindset”, are almost in direct opposition, and I don’t know how to reconcile them.
One possibility is that few students actually attempt to learn the general problem-solving skills that math, CS, and engineering design are rich domains for.  Most are content to learn one tiny skill at a time, in complete isolation from other skills and ideas. Students who are particularly good at memory work often choose this route, memorizing pages of trigonometric identities, for example, rather than learning how to derive them at need from a few basics. If students don’t make an attempt to learn transferable skills, then they probably won’t.  This is roughly equivalent to claiming that most students have a fixed mindset with respect to transferable skills, and suggests that transferability is possible, even if it is not currently being learned.
Teaching and testing techniques are often designed to foster an isolation of ideas, focusing on one idea at a time to reduce student confusion. Unfortunately, transferable learning comes not from practice of ideas in isolation, but from learning to retrieve and combine ideas—from doing multi-step problems that are not scaffolded by the teacher.
“Scaffolding” is the process of providing the outline of a multi-step solution, on which students fill in the details—the theory is that showing them the big picture helps them find out how to do multi-step solutions themselves.  The big problem with this approach is that students can provide what looks like excellent work, without ever having done anything other than single-step work.  De-scaffolding is essential, so that students have to do multi-step work themselves, but often gets omitted (either by the teacher, or by students cheating a little on the assignments that remove the scaffolding and getting “hints”).
I find myself gradually increasing the scaffolding of the material in my textbook, so that a greater proportion of the students can do the work, but I worry that in doing so I’m not really helping them learn—just providing a crutch that keeps them from learning what I really want them to learn.  I don’t think I’ve gone too far in that direction yet, but it is a constant risk.
I’ve already seen students copying material from this blog as an “answer” to one of the problems, without understanding what they are doing—not being able to identify what the variables mean, for example. (I used different notation in class than I used in the corresponding blog post—a trivial change in the name of one variable.)  I’m trying to wean students off of “answer-getting” to finding methods of solution—the entire process of breaking problems into subproblems, defining the interfaces between subproblems, and solving the subproblems while respecting the interfaces.
I do require that the students put together a description of the entire solution to their main assignments—a design report that not only describes the final design, but how the various design decisions were made (what optimizations were done, what constraints dictated what part choices, and so forth).  This synthesis of the multi-step solution at least has the student aware of the scaffold, unlike the fill-in-the-blank sorts of lab report which makes the scaffold as invisible as possible to the student.
I also try very hard for each design problem to have multiple “correct” solutions, though some solutions are aesthetically more appealing than others.  This reduces the focus on “the right answer” and redirects students to finding out how to test their designs and justify their design decisions.
I have been encouraged by signs of problem-solving skills in several students in the course (both this year and in previous classes).  Often it is in areas where I had not set up the problem for the students.  One year, a student came up with a good method for keeping his resistor assortment organized and quickly accessible, for example.  This year, one pair of students used their wire strippers and blue tape as an impromptu lab stand for their thermometer and thermistor, to save the trouble of holding them.
The problems students set themselves often lead to more creative solutions than the ones set for the class as a whole—but how do you set up situations in which students are routinely identifying and solving problems that no one has presented to them?  I believe that the students who identify problems that no one has pointed out to them are the ones who become good engineers, but that attempts to teach others to have this skill are doomed by the very attempt to teach.  Capstone engineering classes are one attempt to get students the desired experience, but I think that in many cases they are too little, too late.

2016 April 4

Banner blooper

Filed under: Uncategorized — gasstationwithoutpumps @ 22:48
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My table banner for the Santa Cruz Mini Maker Faire arrived today from Spoonflower, and it looked really good, until I tried to put it on the table.  I had foolishly ordered a design that was a yard of fabric 56″ wide. The 56″ wide part was reasonable, but the table is most likely only 25–27″ high, so the yard-high pattern is about 50% too big!

I should have thought of that before sending off the order!

Oh, well, perhaps I’ll have a wall behind me that I can blue-tape the banner to.  Or I can put the top foot of it on the table top, though that will make stuff on the table less accessible.

First week’s grading done

Filed under: Circuits course — gasstationwithoutpumps @ 22:44
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I spent all day Sunday grading the first set of lab reports.  I was expecting 24 reports of about 3 pages each, but I got 25 averaging about 5 pages each.  I think that the reports were a bit better this year than at corresponding times in previous years, but I did not get my grading done until almost midnight Sunday night, keeping me from getting much else done this weekend.

(I did manage to get my hair cut and to build a new strobe stand with room for 20 of my LED boards, which should give 1800 lumens during the flash. With a duty cycle of only 1/65, I don’t think that I need heat sinks on the boards for the strobe, as the average current should be only 40mA, though the peak current will be about 2.6A.)

In class on Monday, I gave students some group feedback on their writing, plus a couple of \LaTeX pointers, then took questions, some of which were about writing, but most were about the optimization of the fixed resistor in the voltage divider for the resistance-to-voltage converter in the thermistor lab.  I showed them how to set that up, but did not try to solve it in class.

After class, when I was making up the key (redoing all the problems—I don’t like just looking up results—refreshing my memory on how to solve the problems by resolving them is best), I ran into a little trouble doing the optimization. I used to be able to just ask Wolfram Alpha to solve the differential equation, but their newer parser seems to be much harder to convince to do anything.  I eventually gave up and used a cruder tool to just take the second derivative and solved for the resistance by hand.  That was faster than the time I wasted trying to get Wolfram Alpha to do anything useful.  (I suspect that they have deliberately crippled it, to make people pay for Mathematica.)

Monday afternoon and evening (from about 1:30 to 7:45) was spent grading the first pre-lab homework.  Again the results are a little better than previous years, but there were 9 prelabs fewer than I expected (3 students have dropped already and 6 did not do the prelab).  I hope that those who did not do the prelab were just confused about when it was due, and not starting a trend towards coming to class and lab unprepared. I also hope that no more students drop—this class is not a weed-out class, though it is a lot of work.

Back in January, Mike wanted to know where I ended up doing my grading. Sunday I did my grading in my breakfast room, with the laptop on the floor where I could get to it if I really needed to look something up, but where it was not a constant temptation to goof off.  On Monday, I worked in my office on campus, where the e-mail was a minor distraction that I checked between problems.  (For the prelabs, I graded the entire stack for problem 1, then the entire stack for problem 2, and so forth.  This makes for more consistent and faster grading than grading a student at a time, but it would be faster still if the students didn’t put their answers in random order on what they turned in.) I’ll probably continue with weekend grading in the breakfast room and prelab grading in my office until the distractions get to be too much—then I’ll look for a coffeeshop to grade in.

YouTube closed captions are awful

Filed under: Circuits course — gasstationwithoutpumps @ 13:18
Tags: , , , ,

I looked at the automatically generated closed captions on the Oscilloscope video and they were awful—pretty much just word salad. Speaker-independent voice recognition is obviously not a solved problem at Google.

I could not figure out from the captions what the text was supposed to be, so I’m definitely going to have to take an hour to edit the captions.  For your amusement, here are the automatically generated captions (with time stamps removed):

this

results go and circuits lab

truthful

showing this witness during a self-test
internal calibration began to overshadow

while doing this is the oscilloscope
trunk of an actual protest rally we can

make our nation of this gradually goes
to click here to lower celebration

finals where

whatever settings the previous first
layout which is probably not what you

want once it’s finished it off with
oppressed peoples historical back three

people said these are falling also know
what you want

matter whatever the last person in our
class there will help now also passed a

law received

craftspeople a suitable for calibration
single heads because we were so

impressed you’re the slap on a single
figures out what comes out is to view

that clearly see that is where color
associated with it

channel one yellow peril to this
political channel 39 channel for each

row has little to show you which channel
is for example channel two minutes later

colored chance i’m not respecting the
settings now able to accept this coupled

with 30 measures signal felt craft so
this is where signal from this marker

which is just changed it as a compliment
but this month now throws away and easy

going to take the last year which will
just show us that trust is on the screen

like this property

now to see this listing all we won’t be
using that much bandwidth and landlords

are very very important shows little
light switch when she can be set when

one asks the folks at matthews
telescopes for example tax and you still

think so it will bring up the menu by
pressing his body is still scope sent

along acts now here on the same set to
tax

understand same problem check this
before now also watch now deciding where

around his father is cold six hits and
two bowls bowls permission to just see

they didn’t grade office he’s facing
they’re going about two-and-a-half

divisions so too cold for division

viable single with the slower larger
call for example a change is now five

balls for division and we can see the
same no only goes up by one division in

the other direction to one whole
provision

signal goes off you might rather
increased number of major producing

science able to close at present the
many long now playing here next 10

microseconds

horrible for his own vision for vertical
sets for all channels

provision a single all this way for
division last thing they apparently

because the other way to increase I’m
provision shrinking the way we did not

see one single this way every one
division so this is one killers we’re

also do this population 44122 color
calibration on the east coast is

slightly off

is it about fifteen years

channel as well you just said to
channels on here in great numbers if we

wanted to try to channel off push button
again while standing around a nice

things

orders probe is not properly compensated

just get there is very little space
heater which we can trust is a very

small screwdriver slotted over shooed
and other causes around the corner we

get it just right now include role is

channel on it for

which will help us all based on the
sound levels in the road below ground

connection between the microphone
amplifier board here has the microphone

in silver amplifier chip in black and
some connections on the screw terminal

we have power

5 volts red and brown and black it is
very important to always use this

convention for power and ground so that
you don’t actually connector on things

we don’t have the output signal here in
purple and everything is connected to

these heavier bands which have alligator
clips to the power supply we’re not

going to connect our protocol but we
could have to ground lead to the ground

and probably get here to center panel
which is the signal that is a kind of

difficult connection to make now it’s
connected and we can see on the screen

the output of the mic channels now just
a distraction in the range goals

overseas buyer has your rivals lot we
can also notice that occasionally take

notice cause they saw your head

only when the signal go from below 212
above 2.4 liter just this the trigger

man but other than that shows a trigger
which means it is based on a single

going from their low point for both
point to low is actually separate slope

is rising at going global

another option

trick or treating just normal several
times which will only trigger this is

more useful to wear a lot of things that
you don’t know the exact true that many

levels

sure the level at which is to tax low on
the screen

levels for single trigger a tad bit
lower

usually get a trigger but it’s a free
set a closer Trevor so we had a simple

Update 2016 April 6: After about 5–6 hours of work, I got the closed captions fixed, so these amusing automatic ones are no longer on the video.  Editing the captions is even more work than editing the video, so I can see why so many people don’t bother!

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