20.46 29.80 11.40 14.86 11.90 27.10 16.51 8.81 20.46 14.90 33.67 30.91 14.00 15.35 9.72 19.80 14.86 8.09 10.30 18.30 (a) Find the sample mean. The sample mean is. (Round to two decimal places as needed.) (b) Find the sample standard deviation. The sample standard deviation is. (Round to two decimal places as needed.) (c) Construct a 80% confidence interval for the population mean u. The 80% confidence interval for the population mean µ is ( L : (Round to two decimal places as needed.)

Features Features Normal distribution is characterized by two parameters, mean (µ) and standard deviation (σ). When graphed, the mean represents the center of the bell curve and the graph is perfectly symmetric about the center. The mean, median, and mode are all equal for a normal distribution. The standard deviation measures the data's spread from the center. The higher the standard deviation, the more the data is spread out and the flatter the bell curve looks. Variance is another commonly used measure of the spread of the distribution and is equal to the square of the standard deviation.