What is a crucial step in troubleshooting that helps establish baseline performance for an installation?

Establishing baseline performance is essential in troubleshooting because it allows you to compare current performance against expected standards, helping to identify any issues that may arise during operation. Verifying signal levels and quality at the tap serves as a fundamental step in this process. It measures the integrity and strength of the signals as they enter the system, which directly impacts overall performance.

By checking the signal levels, you can determine if they are within acceptable ranges, indicating that the system is operating effectively. Analyzing these metrics provides insights into potential problems, such as signal degradation or interference, which can negatively affect the overall communication quality.

The other options, while important in their own contexts, do not specifically focus on establishing that crucial baseline of signal performance. Checking cable connections is essential for ensuring physical connectivity but doesn't provide quantitative performance data. Testing the power supply voltage verifies if the hardware is receiving proper voltage but does not directly relate to data transmission performance. Running a complete hardware diagnostic may uncover issues within the equipment but also doesn’t establish baseline performance metrics specifically related to signal quality and levels.