Question

The following table presents 20 observations on cycles to failure of an aluminum alloy test coupons subjected to repeated alternating stress of 15,000 psi at 20 cycles/sec. Construct a normal probability plot, a lognormal probability plot, and a Weibull probability plot of these data. Allow Minitab to estimate the best fit parameters for each distribution. Based on the plots and associated Anderson-Darling (AD) fit statistics, identify which distribution seems to be the best fit model for cycles to failure for this aluminum alloy.

8078 1893 2562 19041 15504 6227 9245 6168 9438 17081 3407 1334 7971 13912 6861 6770 1891 12551 2074 21997

Answer 1

The Normal Probability Plot is as follows:

The Lognormal Probability Plot is as follows:

The Weibull probability plot is as follows:

The Weibul Probability plot is best fit model for cycles to failure for this aluminium alloy. The Weibull probability plot indicates that the Weibull distribution does in fact fit these data well.