A quality control engineer is in charge of the manufacture of computer disks. Two different processes can be used to manufacture the disks. He suspects that the Kohler method produces a greater proportion of defects than the Russell method. He samples 150 of the Kohler and 200 of the Russell disks and finds that 27 and 18 of them, respectively, are defective. Assume thatKohler is designated as "Group 1" and Russell is designated as "Group 2".

Referring to the information above, construct a 95% confidence interval estimate of the difference in proportion between the Kohler and Russell disks that are defective.Thelowerbound of the interval is _______(to 2d.p.)