Explanatory Troubleshooting

When something has gone wrong (or continues to go wrong), we refer to an investigation into the cause of the problem as “explanatory troubleshooting”. We look to explain betrayed expectations in the interests of preventing a future betrayal, or to clear up confusion about what has happened. Troubleshooting starts when we stop thinking something is a mistake and start thinking it’s a problem.

In our ongoing example of the car that won’t start, we have exercised a skill at explanatory troubleshooting. So far, we have simply been interested in why the car won’t start, which amounts to an explanation of the not-starting, which we call a conditional anomaly.

Let’s develop a new example in which we introduce evidence that rules out rival answers.

Example 2.4.1
Failed Streaming
You’ve just moved into a new flat and you’ve had internet service connected. You set up your wi-fi enabled television with streaming video apps. You turn on the television, set up the wi-fi, start up an app, and nothing happens.
The fact that nothing happens stands in need of explanation, as it is a conditional anomaly. You launch an investigation.
LQ: Why won’t the television stream shows?

We already have resources: You’ve turned on the television, so you know there’s power. You’ve connected to the wi-fi router, so you know that link in the internet chain is intact. However, this leaves the possibility of communication problems between the router and the internet service provider. Additionally, it’s worth noting that many apps require registration of some sort before use. Let’s list these explanatory resources.

ER1: The television has power.
ER2: The television is connected to the wi-fi router.
ER3: Many apps require registration and login information.

With this, we can invent lots of possible answers to the LQ.

RA1: The video streaming app is not functioning.
RA2: The connection between the router and the internet is bad.
RA3: The video streaming provider has connection problems.
RA4: You need to register for or log into the app.

Of course, there are a wide variety of other possibilities, but we’ll stick with these for simplicity. Our strategy will be to rule out as many as we can by introducing evidence that an answer will need to explain.

We can test the connection between the router and the internet service provider by connecting with a different device to determine whether that device can access the internet. Let’s imagine it can.

EE1: There is a connection between the television and the internet, through the wi-fi router.

Given this, we can rule out A2.

Next we might use the alternate device to check whether it will stream video from the same source the television is trying to stream video. Let’s say we check that and it doesn’t work.

EE2: The streaming service doesn’t work on another device.

This makes A3 look most likely. Given this, let’s “rank” the rival answers from most likely to least likely: A3 – A4 – A1.

We put A1 last because, given our general understanding of the world, it’s less likely that the app provider has released a broken app than it is likely I have forgotten to log into the app. One imagines the app provider would have noticed such an egregious error by now.

To make A3 even more likely, we might verify with other users that there are problems with the service provider. Let’s say we do this and verify. Then:

EE3: Others are experiencing problems with the streaming provider.

To put it all together:

Example 2.4.2
Failed Streaming, Formalised
LQ: Why won’t the television stream shows?

EE1: There is a connection between the television and the internet through the wi-fi router.
EE2: The streaming service doesn’t work on another device.
EE3: Others are experiencing problems with the streaming provider.

RA1: The video streaming app is not functioning.
RA2: The connection between the router and the internet is bad.
RA3: The video streaming provider has connection problems.
RA4: You need to register for or log into the app.

ER1: The television has power.
ER2: The television is connected to the wi-fi router.
ER3: Many apps require registration and login information.

BE: The television won’t stream shows because the video streaming provider has connection problems.

Next, let’s develop an example of a systematic anomaly.

Example 2.5.1
Mark’s Squeaky Bicycle
My friend Mark’s bicycle is making a squeaking noise that seems louder when he pushes the cranks harder. That seems enough to launch an investigation:
LQ: What is causing the squeak in Mark’s bicycle?
EE1: There is a squeak in Mark’s bicycle.
EE2: The squeak gets louder when he applies more force to the pedals.

We should note first that squeaks on bicycles are notoriously difficult to troubleshoot, partly because:

ER1: Sound carries easily through bicycle frames.

(Note this is an explanatory resource born of experiences in the world.) Given this and no further information, we might guess at a few answers:

RA1: Worn crank bearings
RA2: Loose seat post
RA3: Worn wheel bearings

Our next course of action should be to eliminate possibilities. One easy test is to try cranking the bicycle while seated, listening for the suspicious squeak, then comparing cranking while standing up out of the seat. Mark did this and he determined:

EE3: The squeak happens both when on and off the saddle.

This evidence immediately makes A2 far less likely than the others. If the seat post were the problem, then when Mark wasn’t applying any force at the seat post the squeak would have disappeared.

We ask Mark what kind of maintenance he has done on the bicycle. (Note again this is born of experience: maintenance makes a difference.) He replaced the wheels a while back, but the squeak started after he rode the new wheels for a while. This Explanatory Resource undermines A3. Mark also says he has never done any maintenance on the cranks or on the bearings that allow them to move freely. This fact underwrites A1. Let’s represent these resources as follows:

ER2: The wheel bearings are newer than the crank bearings.
ER3: The cranks have never been serviced.

With this evidence and these resources in place, we can safely say that A1 is the best explanation. Let’s put it all together:

Example 2.3.2
The Squeaky Bicycle (formalised)
LQ: What is causing the squeak in Mark’s bicycle?

EE1: There is a squeak in Mark’s bicycle.
EE2: The squeak gets louder when he applies more force to the pedals.
EE3: The squeak happens both when on and off the saddle.

RA1: Worn crank bearings
RA2: Loose seat post
RA3: Worn wheel bearings

ER1: Sound carries easily through bicycle frames.
ER2: The wheel bearings are newer than the crank bearings.
ER3: The cranks have never been serviced.

BE: Worn crank bearings are causing the squeak in Mark’s bicycle.

(We’re happy to report that Mark’s bicycle received a complete service of the cranks and bearings and the squeak disappeared.)

Last modified: Wednesday, 7 February 2018, 9:52 PM