In statistics, a margin of error (or margin for error) expressed the degree of random sampling error or difference in the results of a statistical survey. Colloquially, it also referred to the amount of flexibility one had in achieving their goal.
In 2368, the planet Penthara IV was slowly turning to ice which would result in thousands, maybe tens of thousands of deaths, in a matter of weeks. Lieutenant Commander Geordi La Forge's solution had extremely critical margins of error, but there would be no more threat if successful. If not successful, then every living thing on the planet would perish, resulting in millions of deaths instead. (TNG: "A Matter Of Time")