The article Bone Density and Insertion Torque asPredictors

Chapter 12, Problem 56

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The article Bone Density and Insertion Torque asPredictors of Anterior Cruciate Ligament GraftFixation Strength (The Amer. J. of Sports Med., 2004:14211429) gave the accompanying data on maximuminsertion torque sN ? md and yield load (N), the latter beingone measure of graft strength, for 15 different specimens.Torque 1.8 2.2 1.9 1.3 2.1 2.2 1.6 2.1Load 491 477 598 361 605 671 466 431Torque 1.2 1.8 2.6 2.5 2.5 1.7 1.6Load 384 422 554 577 642 348 446a. Is it plausible that yield load is normally distributed?b. Estimate true average yield load by calculating aconfidence interval with a confidence level of 95%,and interpret the interval.c. Here is output from Minitab for the regression ofyield load on torque. Does the simple linear regressionmodel specify a useful relationship between thevariables?Predictor Coef SE Coef T PConstant 152.44 91.17 1.67 0.118Torque 178.23 45.97 3.88 0.002S 5 73.2141RSq 5 53.6%RSq(adj) 5 50.0%Source DF SS MS F PRegression 1 80554 80554 15.03 0.002Residual Error 13 69684 5360Total 14 150238d. The authors of the cited paper state, Consequently, wecannot but conclude that simple regression analysisbasedmethods are not clinically sufficient to predictindividual fixation strength. Do you agree? [Hint:Consider predicting yield load when torque is 2.0.]