Student's t distribution essentially accounts for the fact that t is often larger than the corresponding z because it is based on estimated variance, which is biased.

Question

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The student's t distribution takes into account the fact that the variance estimate used in the calculation is based on the sample data, which can introduce bias. The t distribution allows for this uncertainty by using the sample size to adjust the distribution shape and produce more accurate confidence intervals and hypothesis tests. Thus, t values are often larger than corresponding z values due to the added uncertainty in the variance estimate.

Student's T Distribution Essentially Accounts for the Fact That T