Question

27. The article "Study on the Life Distribution of Microdrills" J. of Engr. Manufacture, 2002: 301- 305) reported the following observations, listed in increasing order, on dl lifetime (number of holes that a drill machines before it breaks) when holes were drilled in a certain brass allov. 11 14 20 23 31 36 39 44 4750 59 6 65 67 68 71 74 7678 79 81 84 85 89 91 93 96 99 101 104 105 105 112 118 123 136 139 141 148 158 6 168 184 206 248 263 289 322 388 513 a. Why can a frequency distribution not be based on the class intervals 0-50, 50-100, 100-150, and so on? b. Construct a frequency distribution and histogram of the data using class boundaries 0, 50, 100,..., and then comment on interesting characteristics. c. Construct a frequency distribution and histogram of the natural logarithms of the lifetime observations, and comment on interesting characteristics. d. What proportion of the lifetime observations in this sample are less than 100? What proportion of the observations are at least 200?

Answer 1