The effects of series of balanced dietary protein levels on egg production and egg quality parameters in lying hens from 18 through 74 weeks of age were investigated in this experiment. One hundred and forty four pullets were equally assigned to three different protein level series. The results clearly demonstrated that balanced dietary protein level was the limiting factor for body weight, average daily feed intake (ADFI), egg weight, and egg production. As the cost of research increases, mathematical models become valuable tools to answer research questions. A major application of mathematical modeling is accurate estimation of production performance, growth, and feed consumption for poultry research and production. Different models have been proposed to fit those curves. To test differences of fitted curves, the sum of squared reduction test is used. The results of repeated measures using response variables are appealing.