Blue Flower

Process Tracing

Process tracing is a technique for thinking about whether a change has happened because of an intervention, and perhaps even could only have happened because of that intervention.

It is most famous for a) its four levels of tests used to trace the process by which a project has caused change and b) being a bit like the techniques famous literary detectives use, particularly Sherlock Holmes in 'The Adventure of Silver Blaze'.

The four levels of test are as follows:

'Straw in the wind' – a test which affirms that a given hypothesis (say that someone may be involved in a crime because they know the victim) might be relevant, but does not confirm it (e.g. as other suspects might know the victim as well).

'Hoop' – a test which a hypothesis would have to pass for it to be relevant (say that someone involved in a murder would have to have a means, such as a murder weapon, of carrying it out) but which doesn't confirm the hypothesis is correct (as the person might have had the object used as a weapon for entirely innocent reasons).

'Smoking gun' – a test which confirms a hypothesis (it was the butler that did it, the police officer saw him firing the weapon!), but which doesn't entirely eliminate all other possibilities (the pathologist's report found out later that the butler had actually missed and the victim died of a heart attack).

'Doubly decisive' – the namer of the four tests appears to have run out of metaphors here, but basically the final type of test is one which confirms a hypothesis and eliminates all possible other ones at the same time (e.g. the policeman caught the butler firing the gun as the victim was trying to run away from him).

The simplest way to see if these are useful tests to have in your mind when evaluating is probably to skip the slightly complicated formal explanation and just go straight to the story (which is fourteen pages long and reproduced in full starting from page 19 of this PDF.

Note that the illustrative examples to the tests above are made up, rather than drawn from the story, so as not to spoil it if you do want to read it.  If you can solve the case before Holmes does, process tracing is clearly for you!

(For the record, everyone at SERC still thinks it was the butler that did it despite what Holmes says.)