For sample mean x = 150, sample size n = 36 and sample standard deviation s = 40 find 80% confidence interval for population mean. population standard deviation is not known. use formula for one mean t-interval procedure in section 8.4 of etext with t-value from appendix table iv (use column t0.10). 135.6 to 148.4 154.2 to 175.8 141.3 to 158.7 162.3 to 187.5