The number of unhealthy days based on the Air Quality Index for a random sample of metropolitan areas is shown. Construct an 89% confidence interval based on the data. Assume the variable is normally distributed. Use a graphing calculator and round the answers to at least one decimal place. 39 32 10 16 29 24 0 1 23       <  μ  <

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.