Shear strength of rock fractures. Understanding the characteristics of rock masses, especially the nature of the fractures, is essential when building dams and power plants. The shear strength of rock fractures was investigated in Engineering Geology (May 12, 2010). The Joint Roughness Coefficient (JRC) was used to measure shear strength. Civil engineers collected JRC data for over 750 rock fractures. The results (simulated from information provided in the article) are summarized in the accompanying XLSTAT histogram. Should the engineers use the normal probability distribution to model the behavior of shear strength for rock fractures? Explain.