Abstract: An improved procedure for statistically evaluating the performance, precision and/or accuracy, of at least one analytical instrument in a pool of like or substantially like instruments by comparing the performance of the one instrument located in one laboratory with the performance of like instruments in other laboratories. The procedure includes the step of quantitatively analyzing a reference or control specimen of known constituents by each instrument in the pool and collecting the resultant data from the one instrument in the pool and of the pool instruments. The mean data from the one instrument and of the pool instruments are mathematically correlated in a series of statistical equations for computing a novel, sensitive index known as the "Instrument Performance Index" or IPI.

Abstract: An air conditioning system for a building including an air conditioner, a thermostat for controlling operation of the air conditioner, and alternating current electrical control means including circuitry for effectively maintaining operation of the air conditioner and wherein said system comprises a relay including a switch normally closed in the absence of adverse presence of water, at least one water sensor functioning as a switch in the presence of water, and a triac including first and second terminals and a gate, said triac preventing flow of current to the relay and permitting flow of current when the gate of the triac receives flow of an electrical current.

Abstract: Contractible and extensible ladder of the lazy-tong type for attachment to the underside of a swim/dive platform of a boat or to a deck of a boat. The ladder and the swim/dive platform or deck include coacting means so constructed for positioning the ladder in the contracted position under the swim/dive platform or deck for stowage thereof.