55 



5) Spearman rank correlation of nicotine and year, 

 stratified by tar category. 



6) Spearman rank correlation of average nicotine and year, 

 ignoring tar category. (Average nicotine is defined exactly 

 as in analyses 2 and 4 . ) 



Findings were usually that nicotine was increasing with time 

 to a statistically significant extent. Ten out of 12 two-sided 

 p-values were smaller than .05. The two marginal findings were 

 WLS and Spearman's correlation, both computed for all categories 

 averaged together. P-values for H^: There is no change in 

 nicotine level over time are tabled as follows: 



