Mean confidence interval
The t method assumes independent observations from appropriate sampling. It is exact under normality; large samples may allow an approximation, but strong skew, extreme values or dependence can invalidate it. These assumptions are not tested; systematic errors and instrument calibration are not measured.
Confidence level
The confidence level describes method coverage over repeated samples. It is not the probability that the true mean lies in this computed interval, nor an interval containing that percentage of individual observations.
Raw observations
For observations 1, 2, 3: mean = 2, s = 1, n = 3. At 95%, t ≈ 4.302653; the margin is about 2.484138 and the interval [−0.484138, 4.484138]. This demonstrates the formula; it does not validate its assumptions.
Mean, standard deviation and n
Summary mode: no observations, quartiles or data charts have been fabricated.