This question asks for correlation between the outcome (Y=dental hygiene) and the input (X=$$)  one, two,

three and four years after expenditure.  The initial 14 years' data yields 13 complete pairs (N = 13, 11 df) for

the first calculation, and loses one year for each successive calculation.

     (a) Y with X-1    r=0.13,   r²=0.017,  11 df,   t= 0.435    P>.05  ns

     (b) Y with X-2    r=0.81,   r²=0.656,  10 df,   t= 4.368    P<.002 hs **

     (c) Y with X-3    r=0.61,   r²=0.372,   9 df,    t= 2.309    P<.05  ss

     (d) Y with X-4    r=0.13,   r²=0.017,   8 df     t= 0.526    P>.05  ns

     (f)  The greatest association between X and Y occurs at year 2, then declines with yrs 3 and 4.