b) Two-Sided 95% Confidence Interval To construct a two-sided 95% confidence interval for the population mean, we use the sample mean ( x = 191 x =191 seconds), the sample standard deviation ( s = 11.4 s=11.4 seconds), and the sample size ( n = 7 n=7). Given the small sample size, we use the t-distribution for the calculation. The formula for the interval is