Confidence intervals and the t- distribution

Suppose we want to construct the 95% confidence interval for the mean. The standard deviation is unknown, so as well as estimating the mean we also estimate the standard deviation from the sample. The 95% confidence interval is: Impact on confidence intervals The blue area is proportion and for the 95% corresponds to 2.5% X¯ t n1(2.5) ⇥ s p ... ................
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