Planning should involve considering a "worst case" scenario. Planners do this because the "worst case" can happen! The "worst case" is a set of conditions and circumstances that pose the greatest chance of failure in a planning situation when compared to ideal conditions. Worst case is the worst possible environment or outcome out of the several possibilities in planning. Imagining a worst case scenario helps in formulating contingency plans and in setting aside enough reserves to cushion the impact if the event or situation actually occurs. "Let's consider the worst case scenario" is a cliché for thinking about the worst possible future outcome.

Worst case analysis involves identifying causative, state and environmental variables and analyzing what the outcome would be when these variables are most negative. So define negative situations and see how bad the outcomes might be if that situation occurs.

The "worst case" is the worst possible environment or outcome of several possibilities in planning. Imagining a worst case scenario helps in formulating contingency plans and in setting aside enough reserves to cushion the impact if the event or situation actually occurs.