The book is based on a research work whose main findings are variation percentage of efficiency calibration due to some factors. Also to find out the factors which may hamper the perfect experimental results. The researcher will get a lot of information and a new idea of doing work and also how secondary standard samples can be produced. Moreover, a computer software, ETNA, was used and variation of measured results and ETNA results were calculated to see how effective the software at this type of measurements is.