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


P-values 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:10.1186/1471-2288-11-97

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