This is a challenge to blog readers to come up with (or find examples in practice) of good systems to allocate students to parallel sessions based on their preferences. I've just concluded one round of this, and the bidding system I built worked OK, but is not perfect.

The problem: Around 80 students. On 10 days over 4 weeks they will be split into 3-5 different parallel sessions on those days. Many sessions have a cap on the number of students, and more students will have them as a 1st choice than can fit. Some sessions can take many students and won't fill up. The students can express their preference as ranking, or with numeric values.

This is known in the literature as the Allocation problem, and there are various approaches, though none I found seemed to fit just right, either being easy to code or having existing running code. But I am keen on pointers.

The goals:

• Maximize student satisfaction/minimize disappointment. Giving a student their 1st choice is good. Giving 3rd or 4th choices is bad.
• The system must be easy for the students to understand and use.
• Fairness. This has many meanings, but ideally mismatches that can't be avoided should be distributed. If somebody gets a 4th choice one day, they perhaps should have a better shot at a 1st choice on another day.
• It's nice if there's a means of applying penalties to students who violate rules, sneak into sessions etc. Academic violations can result in less chance at getting your 1st choice.
• It should be flexible. Sessions may have to be changed or many not fully finalize until a week before the session.
• It is nice to handle quirks, like duplicated sessions a student takes only once, but where the student might have preferences for one of the instances over another. There may also be pre-requisites, so only students who take one session can have the sequel.
• Things change and manual tweaking can be advised.

Rank sessions in order, 1st come, 1st served

This was used in the prior year. Much like a traditional sign-up sheet in some ways, students could indicate their choices in order. If more students had a session as 1st choice than would fit, the ones who filled out their form first got in. This gave priority over all 10 days and so it was changed to rotate each week to distribute who was first in line.

I often see people say they would like to see solar panels on electric cars, inspired by the solar-electric cars in the challenge races, and by the idea that the solar panel will provide some recharging for the car while it is running and without need to plug it in.

It turns out this isn't a tremendously good idea for a variety of reasons:

The latest JD Power survey on car satisfaction has a very new complaint that has now the second most annoying item to new car owners namely problems with the voice recognition system in their hands-free interface. This is not too surprising, since voice recognition, especially in cars, is often dreadful. It also reveals that most new tech has lots of UI problems -- not every product is the iPod, lauded from the start for its UI.

A new paper on trusted traveler programs from RAND Corp goes into some detailed math analysis of various approaches to a trusted traveler program. In such a program, you pre-screen some people, and those who pass go into a trusted line where they receive a lesser security check. The resources saved in the lesser check are applied to give all other passengers a better security check. This was the eventual goal of the failed CLEAR card -- though while it operated it just got you to the front of the line, it didn't reduce your security check.

The analysis shows that with a "spherical horse" there are situations where the TT program could reduce the number of terrorists making it through security with some weapon, though it concludes the benefit is often minor, and sometimes negative. I say spherical horse because they have to idealize the security checks in their model, just declaring that an approach has an X% chance of catching a weapon, and that this chance increases when you spend more money and decreases when you spend less, though it has diminishing returns since you can't get better than 100% no matter what you spend.

The authors know this assumption is risky. Turns out there is a form of security check which does match this model, which is random intense checking. There the percentage of weapons caught is pretty closely tied with the frequency of the random check. The TTs would just get a lower probability of random check. However, very few people seem to be proposing this model. The real approaches you see involve things like the TTs not having to take their shoes off, or somehow bypassing or reducing one of the specific elements of the security process compared to the public. I believe these approaches negate the positive results in the Rand study.

This is important because while the paper puts a focus on whether TT programs can get better security for the same dollar, the reality is I think a big motive for the TT approach is not more security, but placation of the wealthy and the frequent flyer. We all hate security and the TSA, and the airlines want to give better service and even the TSA wants to be hated a bit less. When a grandmother or 10 year old girl gets a security pat down, it is politically bad, even though it is the right security procedure. Letting important passengers get a less intrusive search has value to the airlines and the powerful, and not doing intrusive searches that seem stupid to the public has political value to the TSA as well.

We already have such a program, and it's not just the bypass of the nudatrons (X ray scanners) that has been won by members of congress and airline pilots. It's called private air travel. People with their own planes can board without security at all for them or their guests. They could fly their planes into buildings if they wished, though most are not as big as the airliners from 9/11. Fortunately, the chance that the captains of industry who fly these planes would do this is tiny, so they fly without the TSA. The bypass for pilots seems to make a lot of sense at first blush -- why search a pilot for a weapon she might use to take control of the plane? The reality is that giving a pass to the pilots means the bad guy's problem changes from getting a weapon through the X-ray to creating fake pilot ID. It seems the latter might actually be easier than the former.