95% and 99% Confidence Interval for the Mean

If CI is the value of the confidence interval reported by the worksheet, the range of values between the sample mean minus CI and the sample mean plus CI is expected to include the true mean of the underlying population 95 percent of the time (for the 95% confidence interval) or 99 percent of the time (for the 99% confidence interval). This formula assumes that the data set is sufficiently large for the central limit theorem to apply.

95% Confidence Interval for the Mean 

99% Confidence Interval for the Mean 

where

tv,a	= the value of the Student's t distribution with v degrees of freedom such that difference between the cumulative probability function evaluated at tv,a and - tv,a is equal to 1- a.
SE	= Standard Error of the Mean

See Also

Data Statistics

Average Deviation

Coefficient of Kurtosis

Coefficient of Skewness

Coefficient of Variation

Critical Value of K-S Statistic at 90%, 95%, and 99% Significance Level

Kolmogorov-Smirnov Goodness of Fit Statistic for Normal Distribution

Mean

Standard Deviation

Standard Error of the Mean

Statistics References

Variance