How To Identify And Address Bias In Your LSL Inventories

By Jared Webb

Every community wants to find and remove every lead water service line in their water system. The necessary first step is creating an accurate lead service line inventory (LSLI), so that you know where to dig, and can properly prioritize where to start.

Since visually inspecting every service line is prohibitively expensive, communities must rely on sampling: inspecting a subset of all service lines in order to begin to make useful educated guesses about the larger truth of the entire water system.

But inherent in sampling is the potential for sampling bias.

Sampling bias makes it challenging to generalize from our sample to the larger population. This is why it’s so important that water systems can recognize and address sources of bias in their lead service line (LSL) inventory process. 

Fortunately, with a little care (and proper statistical tools) we can mitigate sampling bias.