The article "A Probabilistic Model of Fracture in Concrete and Size Effects on Fracture Toughness" (Magazine of Con- crete Res., 1996: 311-320) gives arguments for why frac- ture toughness in concrete specimens should have a Weibull distribution and presents several histograms of data that appear well fit by superimposed Weibull curves. Consider the following sample of size n = 18 observations on tough- ness for high-strength concrete (consistent with one of the histograms); values of p, (i5)/18 are also given. Observation .47 .58 .65 .69 .72 .74 Pi .0278 .0833 .1389 .1944 2500 .3056 Observation .77 .79 .80 .81 .82 .84 P .3611 4167 .4722 .5278 .5833 .6389 Observation .86 .89 .91 .95 1.01 1.04 Pi .6944 .7500 .8056 .8611 .9167 .9722 Construct a Weibull probability plot and comment.