Confounding and the measurement of the MRT off peak initiative

The Singapore government announced a while back that they were going to start an initiative to try to reduce peak period crowds on our public rail system or MRT (Mass Rapid Transit). The initiative involved providing free and subsidised travel for passengers on selected trips during the morning off-peak period.

This initiative kicked off two days ago. Two days on, some people are wondering if it made any difference – trains seem as packed as they were before, and those who were already taking trains during the free travel periods have found little to no difference of the number of passengers from before.

But before we make any conclusions, aside from the fact that it’s only day two and it makes no sense to conclude any result, we have to realise that this initiative kicked in at a time filled with confounding variables.

What we’re trying to measure here is whether the government initiative has worked by reducing peak period travel. So we’re trying to see if there’s a relationship between the [Government Initiative] and [Fewer Peak Period Passengers]; or more precisely, whether [Government Initiative] caused [Fewer Peak Period Passengers].

A confounding variable is an additional variable (one we could and would rather do without) that obscures the relationship of the variables we’re trying to measure, because its introduction impacts the end result. Let me give you an example.

Let’s say there’s a group of people who are hard of hearing. You discover that they love listening to loud music and have, in fact, done so for at least the last five years. You might conclude that listening to loud music makes you hard of hearing.

But let’s say that you then discover that this group of people all used to operate jackhammers, and were subject to loud noises for most of their working lives. Would you be as confident of your conclusion now?

What if these people were in their 80s? Would that change your mind yet again?

Loud music, operating jackhammers, and age can all contribute to hearing loss. Drawing conclusions from this group to make predictions on hearing loss is going to be tough. You just can’t quite single out one cause for hearing loss.

So, as I was saying, any analysis of the MRT rides this week is definitely going to be badly confounded by (at least) the following:

  • People working from home due to the haze;
  • Parents bringing their children overseas as it’s the last week of the school holidays;
  • Children not taking the trains because it’s the school holidays, leading to;
  • People just trying out what it’s like to travel off peak, with the new initiative; and
  • People just trying out what it’s like to travel during peak periods, with the new initiative.

Confounding in business measurement

Confounding is a terrible thing to have when you’re trying to measure cause and effect. I remember having been involved in several performance measurement initiatives, all happening at the same time, designed to improve sales numbers.

The problem with such initiatives is that you could never really know how much of an impact a particular initiative had on the overall sales results. You could know the impact of all the initiatives put together, but any single one would probably have been affected by others because, as mentioned before, they were all happening at the same time.

It’s difficult to get management to agree putting off trying initiatives simply because you want to get a more accurate measurement. It’s like telling a get-rich-quick addict to try only one get-rich-quick scheme at a time to know what really works. It just doesn’t happen.

But when you don’t know what initiative works and what doesn’t, you can’t afford to drop even a single one of them. And juggling all of them can get pretty expensive.

Singapore hits a record high PSI

Singapore has been experiencing a terrible bout of haze lately, with record-setting PSI of 371 recorded earlier this afternoon. The haze had been, in the beginning, quite a welcome break from the dull monotony of everyday Singapore life.

I’d even followed PSI readings as closely as punters would the weekly 4D results.

But as it drags on, I must say that it’s starting to grate on my nerves. I haven’t had a nice, good run for days. And it’s sad when “getting some fresh air” involves hiding in air-conditioned rooms instead of going out.

Walking through the streets feels a little like walking through a nuclear fallout. The atmosphere’s a little heavier, and it feels a little like swimming through water-lite. People talk less (throats are more easily irritated) and visibility is nowhere close to 100%. It was fun for a while. No more.

On theory, practice, and Snowflake Schemas

Just the other day I learnt that the data warehouse I was working on was designed using a Star and Snowflake schema. I’d known enough about them to know that this meant the data was set up on fact and “dimensional” tables, but not much other than that.

So the moment I had some time I went online and looked up definitions, and realised that they were pretty much the way many of the bigger databases I’d done up looked like. I’d been using this schema for the past four years (at least) without my ever realising it. It was like in Le Bourgeois gentilhomme when Jourdain remarks

Good heavens! For more than forty years I have been speaking prose without knowing it.

Which reminded me of something else I read about in Taleb‘s Antifragile: that academia often comes after practice. You can do something your whole life (practice), have it labelled and described as something in theory (academia), and after a while forget that it’d started not as a theory but as an unlabelled, undescribed bit of practice and not as a theory.

Personally, Taleb’s spelling this out gives me much reassurance that we don’t always have to understand something theoretically in order to do something (an activity) well. If I want to run well, or swim well, or program well, it doesn’t necessarily have to follow on from learning the theories of aerodynamics, water viscosity, or binary.

Student loans and how the deed is infinitely stronger than the word

Interesting article giving the perspectives of three people with outstanding student loans and how they’re paying it off.

I’d never been that heavily in debt and I do sometimes wonder what I’d do. Though I cannot say for sure, I do not see myself holding off the payment of loans if I could I help it. But I probably won’t need to theorise much more as in a few years time my mortgage will kick in and it’d be interesting to see if I’d practice what I preach about paying loans off as soon as I can. I cannot say for sure if that’s what I’d do.

That’s the thing about people: they may foresee themselves doing one thing, and saying they’d do it, only to do something else altogether when they really do it. They’d say I’d buy Brand X, definitely and then just as quick go on to buy Brand Y for no other reason than that because they felt like it. That’s definitely something to think about when collecting user responses in surveys and the like when major decisions are going to be made based off of it.