Obs ppv Ratio Obs ppv Ratio 1 160 .996 16 708 .990 2 164

Chapter 13, Problem 13.65

(choose chapter or problem)

Obs ppv Ratio Obs ppv Ratio 1 160 .996 16 708 .990 2 164 .996 17 806 .984 3 178 .999 18 884 .986 4 252 .997 19 526 .991 5 293 .993 20 490 .993 6 289 .997 21 598 .993 7 415 .999 22 505 .993 8 478 .997 23 525 .990 9 391 .992 24 675 .991 10 486 .985 25 1211 .981 11 604 .995 26 1036 .986 12 528 .995 27 1000 .984 13 749 .994 28 1151 .982 14 772 .994 29 1144 .962 15 532 .987 30 1068 .986 Transverse cracks appeared in the last 12 prisms, whereas there was no observed cracking in the first 18 prisms. a. Construct a comparative boxplot of ppv for the cracked and uncracked prisms and comment. Then estimate the difference between true average ppv for cracked and uncracked prisms in a way that conveys information about precision and reliability. b. The investigators fit the simple linear regression model to the entire data set consisting of 30 observations, with ppv as the independent variable and ratio as the dependent variable. Use a statistical software package to fit several different regression models, and draw appropriate inferences.