Simple regression was employed to establish the effects of childhood exposure to lead. The effective sample size was about 122 subjects. The independent variable was the level of dentin lead (parts per million). Below are regressions using various dependent variables. (a) Calculate the t statistic for each slope, at significance level = 0.01. (Round your answers to 2 decimal places. Negative values should be Indicated by a minus sign.) Dependent Variable R2 Estimated Differ from 0? Slope Standard Error tcalculated p-value Highest grade achieved 0.050 -0.02 0.008 0.002 Reading grade equivalent 0.114 -0.072 0.019 0.000 Class standing 0.050 -0.008 0.008 0.263 Absence from school 0.078 2.700 1.550 0.084 Grammatical reasoning 0.068 0. 185 0.079 0.021 Vocabulary 0.114 -0.290 0.083 0.000 Hand-eye coordination 0.043 0.098 0.035 0.005 Reaction time 0.016 10.200 8.340 0.277 Minor antisocial behavior 0.040 -0.414 0.390 0.302 (b) It would be inappropriate to assume cause and effect without a better understanding of how the study was conducted. O No O Yes