Month: September 2008

Xylophones and zebras part II: learning Spanish

Posted on by John

Here’s an example related to my previous post on xylophones and zebras.

I’ve been listening to Spanish With Michel Thomas in my car lately. These CDs are very different than the academic foreign language classes I’ve taken. Thomas emphasizes the regularities, not the exceptions. For example, he may give some rule and explain that around 3,000 words follow the pattern but there are 3 minor exceptions. He says what the exceptions are, but doesn’t dwell on them. In the classes I’ve taken, those 3 exceptions would certainly be on an exam and the 3,000 words that follow the rule would not.

There is a kind of logic to focusing on the exceptions, especially if the purpose is to assign grades rather than to actually teach people to use a foreign language, but it doesn’t build confidence. I feel like Michel Thomas is trying to increase my confidence and get me speaking the language as quickly as possible. That was definitely not the feeling I had when studying French in college.

Related posts

How much do you expect to learn from that experiment?

Posted on by John

Bayesian statisticians often talk about models “learning” as data accumulate. Here’s an example that applies information theory to quantify how much you can learn from an experiment using the same likelihood function but two different priors: a conjugate prior and a robust prior.

Here’s an example from a paper Luis Pericchi and I wrote recently. Suppose X ~ Normal(θ, 1) where the prior on θ is either a standard Cauchy distribution or a normal distribution with mean 0 and variance 2.19. (The variance on the normal was chosen following an example by Jim Berger so that both priors put half their mass on the interval [-1, 1].)

The expected information gain from a single observation using the normal (conjugate) prior was 0.58. The corresponding gain for the Cauchy (robust) prior was 1.20. Because robust priors are more responsive to data, the expected gain in information is larger (in this case twice as large) when using these priors.

Related: Quantifying information content

Depend on objects, not their presentation

Posted on by John

The most recent blog post by Jeffrey Snover emphasizes that PowerShell pipes objects, not text. When you use single PowerShell commands, you can get the impression that they output text. But everything is an object until the pipeline spills onto the command line.

In UNIX, text output is effectively a programming contract because that is what the whole system is built upon. One command outputs text and other programs know what to expect so they parse the text to get the appropriate data elements so that they can code against it. In this model, if you change the text output of a command—you run the risk of breaking a bunch of scripts. … In PowerShell … We reserve the right to radically change our text rendering to improve our customer experience.

(Emphasis in the original.)

The object interfaces won’t change, but the text rendering probably will.

Xylophones and zebras

Posted on by John

Here is a quote that was on my cup of coffee this morning.

When I was young I was mislead by flash cards into believing that xylophones and zebras were much more common.

(Amy-Elyse Neer, Starbucks “The Way I See It” #297)

Xylophones and zebras are harmless when teaching children the alphabet, but there’s a tendency for teachers to keep throwing in xylophones and zebras — rare examples included for the sake of completeness — from preschool through graduate school. I was preparing for a class I’m teaching tomorrow when I read the quote, and so I had to ask myself whether I am giving xylophones and zebras more attention than they deserve.

One problem with xylophones and zebras is that a student’s difficulty may be the opposite of what the teacher imagines. The preschool teacher who thinks she’s teaching children about the letter “X” may be teaching them about xylophones instead. That’s not necessarily bad; children need to learn about xylophones sometime. But sometimes when we think someone doesn’t understand the idea we’re trying to convey, they get the big idea but don’t get our illustration.

Magnetic cows

Posted on by John

Scientific American had a podcast a few days ago that said cows tend to either face north or south. The people who came to this conclusion studied Google Earth photos of cows (!) and noticed how they tend to line up. This is the first suggestion of a magnetic sense in large mammals.

Some other posts about Scientific American podcasts:

Top three iPod troubleshooting tips

Posted on by John

I really enjoy my iPod, but it’s hardly perfect. Here are my top troubleshooting tips.

  1. Open iTunes before trying to sync your iPod with your desktop. It usually works if you plug in your iPod before opening iTunes, but you can’t count on it.
  2. If you can’t get iTunes to recognize your iPod after several attempts, reboot your desktop and try again.
  3. When your iPod is locked up, you can reboot it by holding the middle and top (menu) buttons down at the same time for maybe 10 seconds.

You do pay for what you don’t use

Posted on by John

Modern operating systems are huge, and their size comes at a cost. When I worry out loud about the size of operating systems (or applications, or programming languages) I often get the response “What do you care? If you don’t like the new features, just don’t use them.” The objection seems to be that you don’t pay for what you don’t use. But you do. Every feature comes at some cost. Every feature is a potential source of instability. Every feature takes up developer resources and computer resources. Often the extra cost is worth it for the extra benefit, but not always. And costs can be more subtle than benefits.

Suppose a developer has a great idea for a new feature. He’s so excited that he puts in voluntary overtime to develop his feature, so the cost of his extra contribution is zero. Or is it? Not unless his enthusiasm spills over to everyone else involved so that they volunteer overtime as well. The testers, tech writers, and others who now have more work to do because of this feature are unlikely to be as excited as the developer.  What was a labor of love for the developer is just plain labor for everyone else. So the new feature now takes a little time away from everything else that needs to be documented, tested, and otherwise managed, diluting overall quality.

This post was prompted by a discussion with Codewiz in the comments to his post about his woes recovering operating system problems. Along the way he mentioned a remarkably stable FreeBSD server he had and attributed its stability to the fact that he never installed any GUI on the box. Lest anyone think that only the Unix world would create a minimalist operating system, take a look at Windows Server Core. Microsoft also realizes that the features that aren’t there can’t cause problems.