"Percent confidence" is a phrase used to express how certain or sure someone is about something. It represents the level of belief or trust someone has in a particular outcome, where the percentage indicates the degree of certainty. Full definition
Regardless, even the possibility of this small an impact can be rejected with at least 90 percent confidence in 6 of our 12 school systems with reasonably precise results. (educationnext.org)
Green vertical bar is estimated 95 percent confidence range (two standard deviations) for annual temperature change. (realclimate.org)