14. Suppose that a certain brand of light bulb has a mean life of 450 hours and a standard deviation of 73 hours. a. Would it be unusual for a light bulb to have a life span of 320 hours? 615 hours? Justify each response. b. A histogram indicates that the sample data follow a normal distribution. According to the Empirical Rule, 99.7% of the light bulbs have a lifetime between what two values? c. Assuming the data are bell-shaped, determine the percentage of light bulbs that will have a life between 304 and 596 hours. 15. The following data represent the number of text messages sent per day for a sample of high school students. Number of text Number of Students messages 80 89 107 90 99 11 100 109 1 a. Approximate the mean number of text messages sent per day. (Round to one decimal place and include units in your response.) b. Approximate the standard deviation in the number of text messages sent per day. (Round to two decimal places and include units in your response.) c. What is the class width of this data set? d. Is it unusual for a student to sent 100 or more text messages per day? Justify your response