Problem 9 It is conjectured that the sound-level readings (in decibels) from street traffic during a specific time period will possess a normal distribution. To test the hypothesis, the following frequency distribution is obtained Class 74 Frequency 4 24 35 15 8 4 Is the hypothesis sustained by the x test at the 5% significance level ? [Hint: to estimate the mean and variance, use the midpoint of each bin as the actual measured value. For the two outer bins, use the boundary of the bin as the actual measured value]