problem-3.17

problem-3.17  The plot can be made with the commands
> attach(twins)
> plot(Foster, Biological)
> detach()
    
Based on this, a guess of 0.8 for the Pearson coefficient and a similar value for the Spearman coefficient seem reasonable. A check can be done with
> cor(Foster, Biological)
[1] 0.882
> cor(Foster, Biological,method="spearman")
[1] 0.8858