What is not a method that may be used to improve the signal-to-noise ratio?

Increasing the amplification of the test instrument serves to boost the overall signal, but it also amplifies the noise present in the system equally. This can lead to a poor signal-to-noise ratio, as the noise becomes more prominent relative to the desired signal.

In contrast, methods that focus on selecting frequencies that minimize noise, improving the fill factor, or adding filter circuits are aimed specifically at either enhancing the desired signal or reducing the inherent noise. Each of these methods addresses noise reduction in a way that can significantly improve the signal-to-noise ratio, making them more effective in achieving clearer and more reliable measurements.