Statistics for Studies on Pesticide Use Knowledge and Practices of Small-Scale Onion Producing Farmers in Controlling Onion Thrips, Thrips Tabaci Lindeman (Thysanoptera: Thripidae), on Onion, Allium Cepa L, and Analysis of Organochlorine and Organophosphate Pesticide Residues in Onion in Kewet District, Central Ethiopia