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.
(b) From the p-values, which slopes differ from zero at α = .01?
(c) Do you feel that cause and effect can be assumed? Do a web search for information about effects of childhood lead exposure.

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Dependent Variable R Estimated Slope Std. Error p-value -0.07 -0.070 0.009 0.018 0.003 Highest grade achieved 061 Reading grade equivalent 121 Class standing Absence from school Grammatical reasoning Vocabulary Hand-eye coordination Reaction time Minor antisocial behavior 025 2 039 071 051 108 043 025 2 -0.006 4.8 0.062 0.032 0.018 6.66 0.36 012 -0.124 0.041 11.8 020