The article "The Load-Life Relationship for M50 Bearings with Silicon Nitride Ceramic Balls" (Lubrication Engr., 1984: 153-159) reports the accompanying data on bearing load life (million revs.) for bearings tested at a 6.45 kN load. 47.1 68.1 68.1 90.8 126.0 146.6 229.0 240.0 103.6 103.6 106.0 106.0 115.0 240.0 278.0 278.0 289.0 289.0 367.0 385.9 392.0 505.0

a. Construct a normal probability plot. Is normality plausible?

b. Construct a Weibull probability plot. Is the Weibull dis- tribution family plausible?