Step 6 2 We found x 0.025 = 32.852 and X 0.975 = 8.907. Recall the sample standard deviation s = 3, and sample size n = 20. Substitute these values to first find the lower bound for the confidence interval of the population variance, rounding the result to two decimal places. (n - 1)s lower bound = 2 X a / 2 (20 - 1)32 Now substitute these values to find the upper bound for the confidence interval of the population variance, rounding the result to two decimal places. (n - 1)s upper bound 2 X 1 - a/2 (20 - 1)32