Dose-response relationship of lung cancer to amount smoked, duration and age starting

Table 14 Age of starting to smoke by current smokers - observed and fitted lung cancers for the linear and best power model, with β₁ fitted separately for each block

Age of starting (yr)	Observed1	Fitted2
		Linear model	Best power model
< 16	1304.92	1294.48	1387.73
16 to < 20	1964.76	1906.55	1921.20
20 to < 24	1227.48	1266.99	1216.48
25+	2173.90	2219.26	2122.14
Never smoked	894.41	878.20	917.92
Total	7565.47	7565.47	7565.47
Fit statistic3		4.77	9.75

¹Observed pseudo-number of lung cancer cases, summed over blocks;

²Fitted pseudo-number of lung cancer cases, summed over blocks. For each study, the fitted number of cases for each block is calculated from the numbers at risk and the fitted relative risks for age of starting to smoke, derived from the fitted value of β₁;

³Based on summation of (observed-fitted)²/fitted, the summation also including terms for the observed and fitted total numbers of controls (not shown). The statistic can be considered to be approximately chisquared distributed on 6 df and is not significant (P > 0.1) for both models.