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Table 4 Estimated means of follow-up variable; population mean = 0.00

From: Attrition and generalizability in longitudinal studies: findings from a 15-year population-based study and a Monte Carlo simulation study

  30% attrition rate 50% attrition rate 70% attrition rate
Dependency Estimate (95% C.I.) 95% coverage Estimate (95% C.I.) 95% coverage Estimate (95% C.I.) 95% coverage
y x
.00 .00 .00 (−.08,.08) 94 .00 (−.08,.08) 94 .00 (−.12,.12) 93
.10 .00 -.05 (−.13,.03) 75 -.08 (−.16,.00) 54 -.12 (−.24,.00) 47
.20 .00 -.10 (−.18,-.02) 22 -.16 (−.24,-.08) 5.4 -.23 (−.35,-.11) 3
.30 .00 -.15 (−.23,-.07) 2.6 -.24 (−.32,-.16) 0 -.35 (−.47,-.23) 0
.40 .00 -.20 (−.28,-.12) 0 -.32 (−.40,-.24) 0 -.46 (−.56,-.36) 0
.10 .10 -.06 (−.14,.02) 70 -.09 (−.17,-.01) 48 -.13 (−.25,-.01) 39
.20 .10 -.11 (−.19,-.03) 18 -.17 (−.25,-.09) 3.8 -.24 (−.36,-.12) 1
.30 .10 -.16 (−.24,-.08) 2 -.25 (−.33,-.17) 0 -.36 (−.48,-.24) 0
.40 .10 -.21 (−.29,-.13) 0 -.33 (−.41,-.25) 0 -.48 (−.58,-.38) 0
.20 .20 -.11 (−.19,-.03) 14 -.18 (−.36,-.10) 2.6 -.25 (−.37,-.13) 1
.30 .20 -.16 (−.24,-.08) 1 -.26 (−.34,-.18) 0 -.37 (−.49,-.25) 0
.40 .20 -.21 (−.29,-.13) 0 -.33 (−.41,-.25) 0 -.49 (−.59,-.39) 0
.30 .30 -.17 (−.25,-.09) 1 -.26 (−.34,-.18) 0 -.38 (−.60,-.16) 0
.40 .30 -.22 (−.30,-.14) 0 -.34 (−.42,-.26) 0 -.50 (−.60,-.40) 0
.40 .40 -.22 (−.30,-.14) 0 -.35 (−.43,-.28) 0 -.51 (−.61,-.41) 0
  1. Dependency = direct effect (β) of study variables on Liability of attrition. Y is dependency between attrition and Follow-up outcome (path c in Figure 1), x is dependency between attrition and Baseline predictor (path b in Figure 1). N in the original sample is 1000. The association between Baseline predictor and Follow-up outcome is β = .10. 95% C.I. = 95% confidence interval. Parameter estimates and 95% C.I.s are average results over the 500 generated samples. 95% coverage = proportion of the 500 samples where the 95% confidence intervals contain the population value. The dependency between study variables and the continuous Liability of dropping out is reported in βs. The corresponding ORs of the associations between study variables and a dichotomized drop-out variable would be about the following (depending on attrition rate): β =.00 equals OR =1; β =.10 equals OR = 1.22; β =.20 equals OR =1.49; β =.30 equals OR =1.82; β =.40 equals OR = 2.23.