Computing Confidence Intervals
• First compute sample mean and sample variance.
• Then T has Student's t-distribution with n − 1
degrees of freedom, where
Computing Confidence Intervals (2)
• To calculate a 90% confidence interval for
where c is the 95th percentile of this distribution.
• As a result,
How Is c Computed?
• The sample mean, variance and n are available from
• c is obtained from Student’s t-distribution tables
available in most textbooks on statistics and online.
• Example: given n = 10 samples and a confidence
interval of 95%, c = 2.262.
• In summary, the confidence interval is computed as