We use the t distribution to construct a confidence interval for the population mean when the underlying population standard deviation 16 is not known. Under the assumption that the population is normally distributed, find ta/2, af for the following scenarios. (You may find it useful to reference the t table. Round your answers to 3 decimal places.) ta/2, df 3 a. A 95% confidence level and a sample of 8 observations. points b. A 90% confidence level and a sample of 8 observations. c. A 95% confidence level and a sample of 28 observations. d. A 90% confidence level and a sample of 28 observations. eBook Print References