plete parts a through c below etermine the critical value s for a right tailed test of a population mean at the a nificance with 15 degrees of freedom etermine the critical value s for a left tailed test of a population mean at the a ficance based on a sample size of n 20 etermine the critical value s for a two tailed test of a population mean at the a ficance based on a sample size of n 14 rit rit Round to three decimal places as needed Round to three decimal places as needed