Based on your answers to Problems 8.85 and 8.86, compare mean full-scale IQ between the exposed and the control groups, after the exclusion of outliers?

Environmental Health, Pediatrics

Refer to Figure 8.12 (p. 313) and Table 8.7 (p. 305).

Figure 8.12: Stem-and-leaf and box plots of full-scale IQ by group, El Paso Lead Study

 

Table 8.7: Comparison of mean finger-wrist tapping scores for the exposed vs. control group using PROC TTEST of SAS

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(a) Control group (b) Exposed group Leaf Вохplot Leaf Boxplot Stem Stem 14 13 13 2 12 58 12 558 3 11 11 11 124 10 55677778 10 011244 5 10 10 01144 15 678 566666667789999 3 10 123444 0111222334 5555666677888999 16 55568889 8 4 8 0004 0002233 | 566666778 5567899 4 0234 12 5 5 5 4 6. --+----+----+ +----+----+ +-- Multiply Stem.Leaf by 10**+1 Multiply Stem.Leaf by 10**+1 %23 3. The SAS System The TTEST Procedure Variable: maxfwt group Mean Std Dev Std Err Minimum Maximum Control 64 54.4375 12.0566 1.5071 13.0000 84.0000 Exposed 35 47.4286 13.1558 2.2237 13.0000 83.0000 Diff (1-2) 7.0089 12.4529 2.6180 group Method Mean 95% CL Mean Std Dev 95% CL Std Dev Control 54.4375 51.4259 57.4491 12.0566 10.2698 14.6020 Exposed 47.4286 42.9094 51.9478 13.1558 10.6414 17.2368 Diff (1-2) Pooled 7.0089 1.8130 12.2049 12.4529 10.9201 14.4902 Diff (1-2) Satterthwaite 7.0089 1.6440 12.3739 t Value Pr > |t| Method Variances DF Pooled Equal 97 2.68 0.0087 Satterthwaite Unequal 65.004 2.61 0.0113 Equality of Variances Method Num DF Den DF F Value Pr > F Folded F 34 63 1.19 0.5408