A test device and method for drawing a vacuum relative to an ambient environment. The method allocates processing time between IO operations and background operations for predetermined time slots based on an indicator of processor workload. The guide system can also include an accessory, such as an accessory guide tube through which a medical instrument can be carried external of the endoscope. 15 grams of olefins per gram of naphtha; at least 0. The system calculates a defect size distribution for each defect size in each of the groups, compares the defect size distribution and a predetermined estimation distribution for each of the groups, and calculates a difference.