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Archive for February, 2018

Puzzle (1)

Wednesday, February 28th, 2018

Here is a graph that purports to be a summary of numbers of divorces per 1000 married people between 2009-2016, i.e. the first part of the graph up to 2014 is before same-sex marriage became legal.

divorces per 1000 married people

My immediate thought is that this must be wrong—if every marriage is between a man and a woman, then the numbers of divorces must be equal between men and women. So, could the “per 1000 married people” be the gotcha here? Again, no. It doesn’t say “per 1000 people”, but “per thousand married people”, and so in the era that this is referring to, the number of married men and married women would be identical. This suggests that there is an error in the calculation here; oddly, the graph has identical numbers from 2013 onwards; we might expect some divergence if we carry on with the graph, even simply due to statistical fluctuations the number of same-sex male divorces and same-sex female divorces is likely to be different.

So, what is happening during the 2009-2012 part of the graph? I suspected initially that they have mistakenly used “per 1000 people” on those entries in the graph, rather than “per thousand married people”. But, this is at odds with the numbers from 2013-2016, where the graph is as expected—numbers “per thousand people” will be a lot less than “per thousand married people”, and this huge leap isn’t apparent between the figures for 2012 and 2013. So, what explains it?

I’ll restrain myself from ranting about the heinous sin of connecting discrete values with lines.

Here’s another graph (from this Daily Mail article (ugh!)) that seems to be from the same source and shows a similar error:

another similar graph

Assumptions

Thursday, February 8th, 2018

Sometimes I find myself making an apology in the following form: “Sorry, but I assumed…”. I’ve occasionally been upbraided for this with a response like “Well, you shouldn’t have assumed in the first place, you should have asked.”. There is perhaps something reasonable here—it isn’t good to be presumptuous, and it isn’t good to offer a glossed apology—but, I usually leave such an encounter with a feeling of “Well, that all sounds very reasonable, but in practice we can’t go around constantly questioning and digging into every detail of an interaction; at some point we have to make a pragmatic choice to use background knowledge and assumptions built on our knowledge of social rules and norms, the particular person, and the particular situation.”

Then I realised. When A says to B “I’m sorry, but I assumed…” it is actually a subtle upbraiding of B by A. The less polite version of this is A saying to be “Sorry, but I perfectly reasonably assumed that we were working in our regular framework of norms of communication and our mutual knowledge of each other and the situation, and you unreasonably did something that didn’t fit into those norms and now you seem to be blaming me for making a perfectly reasonable assumption rather than what should have happened which is that you were doing something that was socially or individually uncharacteristic and so you should have proactively given me reasonable information so that I could understand the situation in which we were interacting (innit).”. Of course, this is complicated—one of the reasons that these misunderstandings occur is when A and B think that they are on common ground (what Wittgenstein calls “agreement not in opinions, but rather in form of life”), but actually are working with a different framework.