When a failure data set for a ceramic material processed in a certain facility is analyzed, it is found that the characteristic strength is 327 MPa and the Weibull modulus is 8.75. A nominally identical batch of material processed in a different facility is also tested and found to have essentially the same characteristic strength, but the Weibull modulus is 6.25. At what stress level is the probability of failure equal to 50% for each set of material