Refractory microstructure and phase composition play important roles in the creep resistance of refractories at high temperatures. The production processing causes heterogeneity of refractory microstructure, which affects the determination of representative creep parameters. The present study focused on the statistical study of compressive creep parameters with a limited number of tests. Different sampling approaches were applied to examine the influence of the heterogeneity. A correlation analysis exhibited an evident negative correlation coefficient between the bulk density of specimens and their creep strain rates. The Norton-Bailey creep parameters of the primary creep stage were received with an inverse evaluation method from datasets with different number of uniaxial compressive creep curves under at least two different constant loads. Their mean values and standard deviations were evaluated for different temperatures. The statistical results of the dataset with combined 7 creep curves (out of 9) allow for elaborated considering the microstructural heterogeneity of refractories in the thermomechanical modelling of industry vessels.