What critical value of t* should be used for a 95% confidence interval for the population mean based on a random sample of 21 observations?Find the t-table here.

For a confidence interval based on 21 observations, the degrees of freedom are 21 − 1 = 20. A 95% confidence interval is two-sided, so the critical value is t* = 2.086; choose “t* = 2.086.”

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