August 29, 2018

Welcome to the Wiggle Room

Inspired by Judea Pearl’s new The Book of Why”, and also by Nicky Case’s work on explorables, I’ve started work on a explorable web app.

Pearl talks about wiggling” variables in a causal network to look at their causal effects. As someone brought up on Meccano, this really makes sense to me. It’s a philosophically interesting idea too.

So my new app is called The Wiggle Room. You can explore the causal effect of one or two influence variables on a consequence variable. Or you can just click the blue button to look at examples.

There are two twists:

  1. There are two main sliders - to show not only the level under intervention but the base level — what would happen without the intervention. The intervention is actually the difference or delta” between the two. And the effect on the consequence variable is also a difference — you can see this on the graphs. This helps us to think in differences” which I believe is essential for understanding causal networks like theories of change.

  2. The variables are not modelled using continuous numbers. Instead, they are intensity variables” (this is Daniel Kahneman’s terminology) which I’ve also called lo-hi variables” elsewhere. They vary between a vague minimum and a vague maximum, a bit like a percentage. In the Wiggle Room, I call them percentages because these are familiar to most people.

The Wiggle Room offers pre-sets to construct the different possible functions between (sets of) influence variables and one confluence variables, in the form of influence shapes” for specific links and combination shapes” which govern how these influences are combined.

So these are the features:

Each variable:

  • Type:
    • intensity or true-false, possibly also probabilistic true-false (e.g. a 75% probability that it is true)
    • combined with: normal or with negative, i.e. including a negative bottom half”.
    • = 4 (or 6) possibilities.
    • plus, the base” or non-intervention level of each variable can be specified and optionally the intervention level. In the case of endogenous variables, these levels are calculated rather than specified.

Each influence:

  • Shape:
    • linear, slow-start, quick-start, U-shaped (there could be others, these are the most obvious)
    • combined with: normal or reversed.
    • = 8 possibilities.
  • Strength: 0-100

Just for the consequence variable (in addition to Type):

  • Combination (how the influence variables combine):
    • soft add, hard add, multiply, smallest, largest (there could be others, these are the most obvious - I’ve just implemented similarity)
    • reversed
    • = 8 possibilities
    • strength of (unspecified) residual influences. This is only relevant if the maximum strength of the influence variables is less than 100, i.e. they don’t control it completely. The influence variables share influence between them, so if there are two, with strengths of 80 and 40, the former gets twice the influence of the latter and there is 20 left to explain” with residual influences.

I think these are fairly intuitive. But they give a bewildering variety of different combinations (for two influence variables and one consequence variable, = 4 or 6 times 8, times 4 or 6 times 8, times 8, times 8, times 8, i.e. a minimum of 524288 different cases. And that doesn’t account for different combinations of influence strengths.)

So next time you see someone hasn’t specified the nature of the links leading into a variable in a theory of change, and you’re supposed to guess it, remember there are over half a million possibilities.

Intensity variables

These variables are mostly intensity variables: they can vary between a rough minimum, which we can think of as 0%, and a rough maximum, which we can think of as 100%. In the Wiggle Room you can also find true-false variables, which we see as being a special case of intensity variables. You can think of them as just having the values 0% and 100%. You can also interpret a value like 50% as meaning a 50% chance of the variable being true.

The variable types also do not need to be restricted to intensity and true-false variables. But these have the significant advantage (especially for people working with theories of change) that interventions and their effects can be conveniently expressed as percentages of the total range of the variable in question.

Rubrics

In practice, intensity variables can be constructed presented using rubrics’: by describing (using rich and concrete language) four or five of the different levels they can take, from minimum (0%) to maximum (100%). The use of rubrics is described well elsewhere1. This is a more fundamental and important task than the usual practice of trying to pin down a variable with just a brief title (e.g. inter-ethnic trust”) and then defining it post-hoc and implicitly via the indicators which have been selected for it.

Calculating effects in a causal network: Theorymaker

I think this is a unique explanation of causal effects because it does not rely on statistics - it’s about the causal connections which explain the statistics. Evaluators often have direct (if often unreliable) information about causal effects which have nothing to do with correlations. Stakeholders talk to us about causal links and only rarely about correlations. We need to have a way to process this kind of information, and statistics can’t help us.

In the Wiggle Room we only look at simple Theories, single steps in causal networks from one or two variables to another. In a larger causal network like a Theory of Change, there will be several such connections. With intensity variables, we can easily calculate how causal effects ripple through a network. If an intervention on a variable A has a 50% influence on B, and the resulting effect on B has a 50% influence on C, the direct causal influence of the intervention A on C will be precisely 25%.

So I’m integrating the same algorithm into the experimental version of my existing Theory of Change visualisation tool Theorymaker.

In the existing version you can express causal relationships using indentation:

Happiness
 Relationships
 Money
  Luck
  Qualifications

… and you can add styling like this…

Happiness; colour=orange3
 Relationships
 Money
  Luck
  Qualifications

In the new version, you can actually build a causal model using the same ideas.

Happiness; combination=largest
 Relationships; base=.5; intervention=.8
 Money; combination=multiply
  Luck; base=.5; intervention=.5
  Qualifications; base=.5; intervention=.5

Adding e.g. combination=multiply after a variable changes the way that variable combines its influences.

Logic gates

Rick Davies asked about implementing logic gates. All of them are possible in the new theorymaker algorithm which is at work in the newest versions of https://stevepowell.shinyapps.io/CausalExplorer and https://stevepowell.shinyapps.io/theorymaker3.

The functions are implemented as generalisations which apply to continuous intensity” variables which range between 0 and 1 or 0 and 100% as well as to true-false variables.

So a true-false variable like the ones in logic gates are realised just by considering the values 0% and 100% of an intensity variable. (If you want, you can consider the values in between as probabilities of true-false values or fuzzy set membership. I think the generalisation of these combinations to intensity variables is really interesting in terms of Theories of Change and also much more applicable in the real world than just on/off situations.)

In Causal Explorer, you can select the type true-false” for your variables, but the only thing (at the moment) which changes is the axis labels change to false and true. I might consider a more logic-gate-like display. Then:

  • NOT: with a single influence variable, select reversed” in the consequence variable section.
    • for all the others, you need to click Include second influence variable” and then choose a value from How do the two influence variables combine?”
      • AND: multiply or smallest (and select reversed” for NAND)
      • OR: soft add, hard add, or largest (and select reversed” for NOR)
      • XNOR: similarity (and select reversed” for XOR)

In Theorymaker3, you can type something like this (try copying and pasting the whole lot)

variable; type=true-false #this switches all the variables to true-false rather than intensity: the bar at the bottom of the variables changes to show just two values. 
variable;base=hide # hide the base values

a; combination=similarity # or whichever of the above combinations you want to try
 b; intervention=0 # fiddle with these (set them to 0 or 1) to see what happens
 c; intervention=1 # fiddle with these (set them to 0 or 1) to see what happens

I’ve also chosen functions which are more general in the sense that they can combine any number of variables, not just two (though in Causal Explorer you can’t visualise more than two).

Limitations

These building blocks are certainly not capable of constructing all possible functions, far from it. Alternatives or additions to the influence shapes and the combination shapes are perfectly possible. The R version of Theorymaker provides the possibility to describe a function directly without any reference to these shapes.

You can’t yet have loops in these diagrams - but I am working on it.

Most importantly, these tools are primarily for visualisation, exploring and getting a feel for” possible causal relationships. They shouldn’t be used to try to get spurious certainty (“look, I put in a few vague ideas and numbers came out!“) where there is none. In most real-world cases, a causal chain of more than one or two links will most often have its effects reduced to almost nothing by noise. These tools are supposed to help model this kind of uncertainty.

Thanks

… to Rick Davies for suggesting to add S-shaped / sigmoid to the list of variable shapes, and for the discussion which led me to document the logic-gate possibilities.


  1. King, J., McKegg, K., Oakden, J., & Wehipeihana, N. (2013). Rubrics: A method for surfacing values and improving the credibility of evaluation. Journal of Multidisciplinary Evaluation, 9(21), 11–20. Retrieved from http://journals.sfu.ca/jmde/index.php/jmde_1/article/viewFile/374/373

evaluation theorymaker visualisation
May 8, 2018

Realtime comments on a Theory of Change

Wouldn’t it be great if, for an evaluation, you could map out the project’s theory of change and then pin the data (the answers to the evaluation questions) directly on the diagram as pop-up notes? Ideally with different colours to mark different kinds of respondent (and other data sources). You could use it interactively with respondents, and/or paste the data on later and elicit comments.

I made a mock-up.

You can interact with it here, and view the comments. If you were logged in, you could also update the diagram, add comments etc.

I made it with Realtimeboard, which is really interesting for this task. Disadvantage: There are only 3 colours for the comments.

You can also embed a diagram in a webpage, like this (you have to click on the symbol) -

It updates live, but you can’t see the comments.

nerdvana
May 7, 2018

Responses to open questions shown as tooltips in a chart

Open questions in surveys are a great idea. But often, we don’t really have time to looking at them in detail.

Here’s a suggestion to make more use of data from your open questions.

Suppose you have just implemented a survey on attitudes to public transport, which includes groups of numerical questions on which the respondents rate the local transport system on convenience and value. And suppose you’d thoughtfully added an open question asking for more information on those answers.

Try making a chart with the total or mean scores on the two groups of numerical questions on the x- and y-axes, and add the answers to the open question as a third column to give the tooltips. It encourages the reader to look more closely at individuals who are extreme in one way or the other … who are the people who think the system is convenient but too expensive? And what about the typical” people in the middle?

Of course you can’t have tooltips on a printed document. I believe it’s really tricky in PDF. So it makes most sense to share your document on the internet. Here are some ways to do it, and one way using Excel.

Tableau public

The easiest way to do this is probably in in Tableau Public, as above. Full embed_code_version here.

Tableau Public is a free download - you install the program, work on your chart on your computer then press a button to share it to the Tableau website. You can also embed the chart as I did above (though I had to delete some whitespace in the embeddable code to make it work).

Google charts: HTML

With Google charts you just edit a piece of HTML and paste it into your webpage. It is not too difficult to edit the HTML, but it isn’t so easy to connect it to a database, e.g. a Google sheet. Still, the results are nice. Here I’ve included a third dimension (the sizes of the points — you can do that in Tableau too):

Google Charts in a Google Sheet

There is also a point-and-click version, when you embed a chart within a Google sheet, data connection is trivial but you can’t customise the tooltips so it doesn’t really answer the question I posed in this blog.

Google Fusion Tables

I also tried the same trick in Google Fusion Tables: here’s the template, you can copy it and adjust it to your needs.

However, it doesn’t seem to be maintained any more.

R

If you’re into R, you can do it with htmlwidgets. I found it a bit fiddly though to make the tooltips work.

Excel

You can do something similar in Excel, but you have to publish the workbook as an Excel macro-enabled file, which might scare some people.

Other uses

Rather than using the narrative data as a mere adjunct to the numerical data, you can also turn the method on its head. So you can focus mainly on the narrative answers - the numerical answers might be just e.g. age etc or some other variable which helps to put the narrative answers in context.

Sensemaker® uses some ideas like this too.

code



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