Table 2.
Estimated regression coefficients and standard errors (SE) when no values are missing; when data are missing completely at random; when outcome blood pressure (BP) is missing at random; when covariate (baseline BP) is missing at random; and when outcome BP is missing not at random. When values were missing, multiple imputation as well as the maximum likelihood method were used
Type of missingness | Analysis | Regression coefficients | ||
---|---|---|---|---|
Intercept estimate (standard error (SE)) P |
Baseline blood pressure estimate (SE) P |
Outcome blood pressure estimate (SE) P |
||
No missing values | Complete case analysis | −2.48 (4.69) 0.60 |
1.013 (0.025) <0.0001 |
−50.8 (1.48) P < 0.0001 |
Missing completely at random (MCAR) | Multiple imputation | −6.11 (5.72) P = 0.29 |
1.037 (0.030) P < 0.0001 |
−51.5 (1.78) P < 0.0001 |
Maximum likelihood | −6.85 (5.17) P = 0.18 |
1.041 (0.028) P < 0.0001 |
−51.2 (1.68) P < 0.0001 |
|
Missing at random (MAR) (outcome) |
Multiple imputation | −2.60 (5.15) P = 0.61 |
1.014 (0.028) P < 0.0001 |
−51.0 (1.70) P < 0.0001 |
Maximum likelihood | −2.75 (5.08) P = 0.59 |
1.015 (0.027) P < 0.0001 |
−51.2 (1.65) P < 0.0001 |
|
Missing at random (MAR) (baseline blood pressure) |
Multiple imputation | −6.09 (5.37) P = 0.26 |
1.026 (0.029) P < 0.0001 |
−51.1 (2.16) P < 0.0001 |
Maximum likelihood | −5.49 (5.41) P = 0.31 |
1.026 (0.032) P < 0.0001 |
−50.2 (2.18) P < 0.0001 |
|
Not missing at random (MNAR) (outcome blood pressure) |
Multiple imputation | −8.64 (5.07) P = 0.089 |
1.026 (0.028) P < 0.0001 |
−47.5 (1.99) P < 0.0001 |
Maximum likelihood | −8.13 (5.61) P = 0.15 |
1.026 (0.032) P < 0.0001 |
−47.6 (2.09) P < 0.0001 |
For comparison the results of an analysis of the data without any values missing is also shown