Statistics & probability
Normal interval probability
Find the probability inside and outside an interval under a normal model.
A clear answer. Here’s how.
Standardises each bound and integrates the supplied normal model. Reports probability below the lower bound, inside the interval and above the upper bound. Requires lower ≤ upper and a positive standard deviation. This does not test whether your data follow a normal distribution. Uses floating-point numerical approximations.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Distribution mean
- 0
- Distribution standard deviation
- 1
- Interval lower bound
- -1
- Interval upper bound
- 1
Example result
- Below lower bound
- 0.158655253931
- Inside interval
- 0.682689492137
- Above upper bound
- 0.158655253931