Table 3 

Agreement of reported physical activity, by time between completing identical questionnaires 

Number of women 
Agreement 
Kappa (95% CI) with quadratic weighting 




Time between completing identical questions on the frequency of strenuous activity (average time between the two) 



≤ 6 months (0.3 years) 
238 
64% 
0.71 (0.59  0.83) 
> 6 months  1 year (0.9 years) 
1,224 
59% 
0.61 (0.55  0.67) 
> 1  2 years (1.5 years) 
7,002 
54% 
0.55 (0.53  0.57) 
> 2 years (2.6 years) 
9,153 
52% 
0.51 (0.49  0.53) 
P for trend 
0.03 



Time between completing identical questions on the frequency of any activity (average time between the two) 



≤ 6 months (0.2 years) 
221 
57% 
0.67 (0.53  0.81) 
> 6 months  1 year (0.9 years) 
1,171 
53% 
0.67 (0.61  0.73) 
> 1  2 years (1.5 years) 
6,044 
48% 
0.60 (0.58  0.62) 
> 2 years (2.6 years) 
5,312 
47% 
0.58 (0.56  0.60) 
P for trend 
0.05 



Pvalues for trend in kappa were estimated by weighted least squares regression using the inverse of the variances of the kappa coefficients 

Armstrong et al. BMC Medical Research Methodology 2011 11:97 doi:10.1186/147122881197 