Refractories often show heterogeneous microstructure, which contributes to the scatter of their mechanical properties in laboratory tests. To account for this characteristic, statistical analysis is necessary. The present paper investigates the effect of the heterogeneity of a shaped alumina spinel refractory on its creep behavior. The creep tests were performed at various temperatures and stresses under uniaxial compressive and tensile loads. For each temperature, the combination of different numbers of curves was considered for the inverse estimation of Norton-Bailey creep parameters. The mean value of each parameter and its standard deviation was compared for different combinations of curves, temperatures, and the different loading regimes (uniaxial tension and uniaxial compression). The confidence intervals and residuals were used to determine the representative set of curves for the material creep behavior.