Convert between confidence level, critical value and margin of error.
Raising confidence widens the interval because a larger critical value is required. Moving from 95 to 99 per cent confidence widens the interval by about 31 per cent for the same data. There is no free lunch: greater confidence always means a less precise interval unless the sample grows.
Confidence Level
Critical value is the standard normal z for the two-tailed area; margin of error = z × SE
Critical value is the standard normal z for the two-tailed area; margin of error = z × SE Raising confidence widens the interval because a larger critical value is required. Moving from 95 to 99 per cent confidence widens the interval by about 31 per cent for the same data.
There is no free lunch: greater confidence always means a less precise interval unless the sample grows.
This calculator takes 3 inputs: Confidence level, Standard error, Point estimate. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.