From: Rick Bradbury
Date: 30 Nov 1998
Time: 14:56:32
Remote Name: 141.114.130.70
1) Yes, contractors 2) The individual units are lots of material, say 6000 tons of asphalt pavement, or 150 cubic yards of concrete. 3) Most of the limits are two sided. A couple of criteria are one-sided, having only a specified minimum. 4) In most cases, the unit is percent. % asphalt content, %passing a certain sieve size, % air voids, % air in concrete. PSI for concrete strength is another unit we use. 5) The population is a lot of material, as mentioned before. 6) The tables we use are used by many agencies. I know they are used by Federal Highway Administration in their FP-92 spec. The PWL table is also used by the FAA in their pavement spec. The PWL table was taken from a percent defective table developed in Mil Spec 414, but I am not certain where the Pay Factor table originated. The tables can be seen at our web site at www.state.me.us/mdot/planning/research/106.htm. Some of the formulas on the page are garbled due to formatting problems, but they are basic statistical formulas such as standard deviation and percent within limits, I believe the tables are legible.