Wednesday, 28 April 2010

Marshmallow towers

I wish that I had more time to look at some of the amazing/fascinating talks at TED ( I came across Tom Wujec's short talk about his "Build a marshmallow tower" this week (Thank you to Boing Boing.)
Among the lessons from the research are that successful projects need organising, they need specialist expertise, and that there is great value in iteration, testing and improving. (Note the success of groups with someone with organisational skills, the work of architects, the kindergarten students.)

These lessons apply to O.R. projects as well.
(1) Time spent planning is seldom wasted;
(2) O.R. is not just about techniques; there needs to be experience of project work provided by a broad exposure to O.R. work
(3) the process of O.R. model-building ought to be iterative, with feedback from simple models feeding the refinement of the next development of that model.

Monday, 19 April 2010

O.R. on a trip to London

We went to London for a two-day break last week, and, inevitably, I looked at some of the experience with a pair of O.R.-problem-seeker's spectacles. Two of the things I saw are worth recording.

We went to the theatre (Phantom of the Opera); earlier in the year we had booked online and bought the cheapest tickets on sale ... even for a treat like this, we couldn't face paying some of the prices. The cheapest seats are £25; in Exeter and Taunton, where we generally go to the theatre, the most expensive seats are less than £20. When we got to the theatre, we discovered that the section in which our seats were located was closed for the evening, and we were bumped up to higher quality seats ... in fact the most expensive ones, at £59 each. At no charge, of course. So here is the cheapskate's optimal policy for theatre-going. Book well in advance, for a midweek (less popular) evening, in the cheapest section fof the theatre. Then wait and see what happens when you arrive. At worst, you have your seats. But you may get an upgrade instead. (Oh, and take your own chocolates ... theatre prices are high!)

We bought Oyster cards to pay for the trips around London on the bus and tube. The cost of fares is deducted from the balance on the card, up to a daily maximum, which depends on where you travel and when. So, off-peak, in zones 1-2, the cap is £5.60, which is also the price of a day card. We didn't save much except time with that. We did save when we used the tube in the morning rush-hour. Even then, the scheme has a cap on the day's deduction. Looking at the calculation of caps, we spotted an anomaly. For someone whose use of the system consists of one journay in the morning rush-hour and a number of journeys in the off-peak season, the cap may be more than the combined rush-hour fare and the cost of the day card. So it is better not to use the same Oyster card for the rush-hour and the rest of the day. So here's the optimal strategy for anyone doing this type of day's travelling very often. Have two cards. Use one for the rush-hour, and the other for the wandering about. It depends on what zones you are using, so I am not going to spell out what to do ... an exercise for the reader.

Queues in Nationwide Building Society

I suspect that the problem of queue control is the most obvious area where O.R. has made impacts on everyday life. Certainly, it is the example that I use in my "cocktail-party" explanation of what O.R. models.

Last week, the U.K.'s largest building society, the Nationwide, announced that any of its card customers wishing to withdraw less than £100 would have to use a cash machine (ATM = Automatic Teller Machine). This was an attempt to cut queues. The building society, like most others, offers numerous financial services, such as mortgages, savings accounts and insurance. Already, there are attempts to reduce the queues at the tellers, by filtering the customers according to the type of transaction. In Exeter's branch, there are four tellers, and a single queue, with several assistants on the customer side of the tellers who ask people who are queueing whether their transaction could be handled in some other way.

But the latest move has attracted criticism, as the customers who are most affected are thought to be those who are least comfortable with the ATMs -- the elderly, the disabled .... Maybe those customers could be encouraged to sabotage the scheme by carrying (say) £80, queueing to deposit it, and then withdrawing £100 at once. That way they will get the £20 they need, and without facing the (to them dreaded) ATMs.

Saturday, 17 April 2010

Where does this quotation come from?

We were in a seminar today about God's work in mission and this quotation was thrown into the discussion. It doesn't feature (yet) on Google, so I am putting it here for Google to find!

"If the impossible is not part of our plans, then God is not one of our partners".

What does that have to do with O.R.? Not much, but it is a reminder that O.R. cannot be applied to Christian work because of God's role in it!