Sex is 1 for male and 2 for female.  Drinking use is coded from 1 to 5, with
 1 if less than 1/4 of  drinking water from well and 5 if all drinking water
 from well.  The same code is used for cooking water.  Arsenic levels are in 
 parts per million.    
      Age        Sex       Drinkuse   Cookuse Arswater    Arsnails
 
       44          2          5          5     .00087       .119  
       45          2          4          5     .00021       .118  
       44          1          5          5          0       .099  
       66          2          3          5     .00115       .118  
       37          1          2          5          0       .277  
       45          2          5          5          0       .358  
       47          1          5          5     .00013        .08  
       38          2          4          5     .00069       .158  
       41          2          3          2     .00039        .31  
       49          2          4          5          0       .105  
       72          2          5          5          0       .073  
       45          2          1          5       .046       .832  
       53          1          5          5      .0194       .517  
       86          2          5          5       .137      2.252  
        8          2          5          5      .0214       .851  
       32          2          5          5      .0175       .269  
       44          1          5          5      .0764       .433  
       63          2          5          5          0       .141  
       42          1          5          5      .0165       .275  
       62          1          5          5     .00012       .135  
       36          1          5          5      .0041       .175  

The arsenic data are measurements of arsenic levels of drinking water and
toenails for individuals in New Hampshire with private wells. Consider
prediction of arsenic level in nails from the available predicting variables.
You may transform the data in any fashion that you desire. You should
consider the strengths of association and which variables appear related
to arsenic level in nails. You should develop a formula for prediction of
arsenic level in nails, and you should develop approximate individual 95
percent con_dence intervals for parameters in your prediction equation.