Example 2.13 Refer to Example 2.7 of overtolerance and expanded tubewall reduction. The Minitab output for a linear fit to these data is given below. The regression equation is WR = 3.23 + 215 OT Predictor Constant OT Coef 3.2310 215.30 SE Coef 0.2725 32.41 11.86 6.64 0.000 0.000 S = 0.9553 R-Sq = 65.78 R-Sq(adj) = 64.2% Example 4.11 Consider the national percentages for HIV-related risk groups (Science, 1992) given in Table 4.3. A firm hires a new worker after a national advertising campaign. a What is the probability that the worker falls in the "risky partner" category? b What is the probability that the worker is in at least one of the risk groups? c If the firm hires 1,000 workers, how many are expected to be at risk if the 1,000 came from the population at large? d If the firm hires 1,000 workers, how many are expected to be at risk if the 1,000 come from high-risk cities? Table 4.3 Prevalence of HIV-Related Risk Groups, National and High-Risk Cities Samples Risk Group Multiple partners Risky partner Transfusion recipient Multiple partner and risky partner Multiple partner and transfusion recipient Risky partner and transfusion recipient All others No risk National Percent Number 7.0 170 3.2 76 2.3 55 1.7 41 0.0 1 0.2 4 0.7 1 84.9 2,045 High-Risk Cities Percent Number 9.5 651 3.7 258 2.1 144 3.0 209 0.3 20 0.3 19 0.7 51 80.4 5,539