Establishing a Theory of Probable Cause

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Establishing a theory of probable cause is crucial in troubleshooting, as it helps identify the most likely root of the problem. Technicians gather information from the user, analyze symptoms, and consider possible causes based on their experience and knowledge. A good technician will keep an open mind and reassess the theories based on new evidence. This step may require research, consultation with colleagues, or examination of documentation, and it is a foundation for building the troubleshooting strategy. The theories are then tested in the next steps of the troubleshooting process.

Guide for Establishing a Theory of Probable Cause

CompTIA A+ troubleshooting methodology includes a step known as Establishing a Theory of Probable Cause.

What is it?: A Theory of Probable Cause is essentially a hypothesis of what is causing the problem in a given IT context. This involves gathering information, identifying symptoms, and using your knowledge and experience to pinpoint the most likely cause of the issue.

Why it is important?: This step is critical as it helps in saving time by providing a focused approach to troubleshooting. It also reduces the risk of causing additional problems by making unnecessary system changes.

How it works?: After gathering all the data about the issue, you create a short list of the most likely causes. You then test these theories one-by-one, starting with the most likely and eliminating them until you find the root cause.

Exam Tips:
- When answering questions around this topic, have a systematic approach in your mind.
- Read the question carefully to identify the problem, gather clues from the information provided, and apply your technical knowledge to establish a probable cause.
- Use elimination to narrow down to the correct cause.
- Show your working in exam questions where you need to establish a theory of probable cause. This demonstrates your systematic approach even if the final answer is incorrect.
- Remember that this phase is a part of a larger troubleshooting process. Understanding the overall process will help you answer the question in the context of the steps that come before and after it.

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Question 1

A technician suspects a faulty hard drive in a customer's laptop. How should they test their hypothesis?

Replace the hard drive immediately Run a disk cleanup Run a diagnostic tool on the hard drive Defragment the hard drive

Correct Answer: Run a diagnostic tool on the hard drive

The best approach for the technician is to run a diagnostic tool on the hard drive to test their hypothesis of it being faulty. This will allow them to gather data and information about the drive's health and performance, helping confirm or rule out issues. Replacing the drive prematurely could be unnecessary if the issue lies elsewhere. Running a disk cleanup or defragmentation may help optimize the drive but won't necessarily identify hardware faults that the diagnostic can detect.

Question 2

A technician needs to determine the cause of a printing issue in a networked environment. What should their first step be?

Change the print settings Verify network connectivity from the affected device Delete and re-add the printer Replace the printer

Correct Answer: Verify network connectivity from the affected device

When troubleshooting a printing issue in a networked environment, the first step should be to verify network connectivity from the affected device. This ensures that the device is able to communicate with the network and reach the printer. If there is a connectivity issue, it needs to be resolved before proceeding with other troubleshooting steps. Replacing the printer, changing print settings, or deleting and re-adding the printer should only be considered after confirming that the device has proper network connectivity.

Question 3

A user reports their computer is running slow. What is the best way to establish a theory of probable cause?

Reinstall the OS Ask the user about recent hardware or software changes Remove the graphics card Upgrade the RAM

Correct Answer: Ask the user about recent hardware or software changes

Asking the user about recent changes helps establish possible causes for the issue without making unnecessary changes.

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