COMM-1057EL Chapter Notes - Chapter 12: Confidence Interval, Interval Estimation, Test Statistic
23 Nov 2017
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When the population standard deviation is unknown and the population is normal, the test statistic for. 12-1: inference about a population mean when the standard deviation is unknown. Rather than using , we substitute the sample standard deviation s in place of the unknown population standard testing the hypotheses about (cid:2020) is: (cid:1872)= / . Which is student t-distributed with (cid:2021)= (cid:883) degrees of freedom. Confidence level estimator of when is unknown: estimate and test a population mean. We will no longer use the z-statistic and z-estimator of (cid:2020) These formulas now make obsolete the test statistic and interval estimator employed in ch. When the population is small, we must adjust the test statistic and interval estimator using the finite population correction factor. In populations that are large relative to the sample size, we can ignore the correction factor: large populations are defined as populations that are at least 20x the sample size.
