Abstract: The simple linear correlation coefficient (pearson) is a tool for people who work in statistical analysis. The aim of this study is to determine the required sample size (water level) to estimate the Pearson coefficient of correlation in terms of force and direction of total temperature variables (maximum, minimum). The annual total annual evaporation of Babil governorate was marked by the symbol E for the governorates of Babylon and Najaf during the period from 2011-2017. The result of the association of the total annual maximum temperatures and the total annual evaporation of the province of Babylon is strong and positive as a result of the correlation of the total of the minimum temperatures and the total annual evaporation of the province of Babylon is weak and positive, the total temperature (maximum, minimum) and total annual evaporation of Najaf governorate were weak and negative.