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. From the p-values, which slopes differ from zero at a = .01? (Round your answers to 2 decimal places. Negative values should be indicated by a minus sign.) Estimated Dependent Variable R² Slope Std Error Icalculated p-value Differ from 0? Highest grade achieved 0.013 -0.026 0.020 0.196 (Click to select) Reading grade equivalent 0.128 -0.087 0.035 0.014 (Click to select) Class standing 0.016 -0.010 0.030 0.739 (Click to select) Absence from school 0.066 2.200 1.500 0.145 (Click to select) Grammatical reasoning 0.057 0.178 0.063 0.006 (Click to select) Vocabulary 0.107 -0.209 0.048 0.000 (Click to select) Hand-eye coordination 0.049 0.063 0.040 0.118 (Click to select) Reaction time 0.025 8.000 8.120 0.326 (Click to select) Minor antisocial behavior 0.010 -0.540 0.654 0.411 (Click to select) (b) It would be inappropriate to assume cause and effect without a better understanding of how the study was conducted. No Yes