Exhibit III.b.1. Scenario III, Missing Data Dependent on Post-test: Data Missing for 40% of Students
Imact Estimate | Standard Error of Imact Est. | 90% Cl | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
Data | Pre-test Data Available? | Estimate | True Imact | Bias | Bias Level | Standard Estimate | Unbiased Estimate | Bias | Bias Level | % of Samples in which 90% Cl Contains .20 |
No Missing Data | No | 0.203 | 0.200 | 0.003 | Low Bias | 0.085 | 0.088 | -0.002 | Low Bias 0.892 0.892 | |
Yes | 0.203 | 0.200 | 0.003 | Low Bias | 0.062 | 0.062 | 0.000 | Low Bias | 0.886 | |
A. Pre-Test (X) Data Missing | ||||||||||
Case Deletion | No | 0.133 | 0.200 | -0.067 | High Bias | 0.064 | 0.063 | 0.001 | Low Bias | 0.723 |
Yes | ||||||||||
Dummy Variable Method | No | 0.215 | 0.200 | 0.015 | Low Bias | 0.067 | 0.067 | 0.000 | Low Bias | 0.886 |
Yes | ||||||||||
Mean Value Imputation | No | 0.267 | 0.200 | 0.067 | High Bias | 0.069 | 0.065 | 0.003 | Low Bias | 0.749 |
Yes | ||||||||||
Single, Non-stochastic | No | 0.200 | 0.200 | 0.000 | Low Bias | 0.065 | 0.064 | 0.001 | Low Bias | 0.899 |
Regression Imputation | Yes | |||||||||
Single, Stochastic | No | 0.201 | 0.200 | 0.001 | Low Bias | 0.064 | 0.063 | 0.001 | Low Bias | 0.890 |
Regression Imputation | Yes | |||||||||
Multiple Stochastic | No | 0.201 | 0.200 | 0.001 | Low Bias | 0.065 | 0.062 | 0.003 | Low Bias | 0.903 |
Regrssion Imputation (n=5) | Yes | |||||||||
EM Algorithm with Multiple Imputation (n=5) | No | 0.202 | 0.200 | 0.002 | Low Bias | 0.066 | 0.063 | 0.003 | Low Bias | 0.899 |
Yes | ||||||||||
B. Post-Test (Y) Data Missing | ||||||||||
Case Deletion | No | 0.076 | 0.200 | -0.124 | High Bias | 0.087 | 0.087 | 0.000 | Low Bias | 0.574 |
Yes | 0.113 | 0.200 | -0.067 | High Bias | 0.064 | 0.063 | 0.001 | Low Bias | 0.723 | |
Mean Value Imputation | No | 0.059 | 0.200 | -0.142 | High Bias | 0.053 | 0.087 | -0.035 | Low Bias | 0.261 |
Yes | 0.057 | 0.200 | -0.143 | High Bias | 0.040 | 0.069 | -0.030 | Low Bias | 0.127 | |
Single, Non-stocastic | No | 0.079 | 0.200 | -0.121 | High Bias | 0.088 | 0.087 | 0.000 | Low Bias | 0.592 |
Regression Imputation | Yes | 0.140 | 0.200 | -0.060 | High Bias | 0.064 | 0.063 | 0.000 | Low Bias | 0.758 |
Single, Stochastic | No | 0.080 | 0.200 | -0.120 | High Bias | 0.090 | 0.089 | 0.001 | Low Bias | 0.600 |
Regression Imputation | Yes | 0.141 | 0.200 | -0.059 | High Bias | 0.065 | 0.065 | 0.001 | Low Bias | 0.763 |
Multiple, Stochastic | No | 0.078 | 0.200 | -0.122 | High Bias | 0.095 | 0.087 | 0.007 | Low Bias | 0.632 |
Regression Imputation (n=5) | Yes | 0.139 | 0.200 | -0.061 | High Bias | 0.068 | 0.063 | 0.005 | Low Bias | 0.797 |
EM Algorithm with Multiple Imputation (n=5) | No | 0.080 | 0.200 | -0.120 | High Bias | 0.095 | 0.088 | 0.007 | Low Bias | 0.636 |
Yes | 0.138 | 0.200 | -0.062 | High Bias | 0.069 | 0.063 | 0.006 | Low Bias | 0.800 | |
Weighting - Simple | No | 0.079 | 0.200 | -0.121 | High Bias | 0.088 | 0.087 | 0.000 | Low Bias | 0.588 |
Yes | 0.135 | 0.200 | -0.065 | High Bias | 0.064 | 0.063 | 0.001 | Low Bias | 0.735 | |
Weighting - Sophisticated | No | 0.079 | 0.200 | -0.121 | High Bias | 0.088 | 0.087 | 0.000 | Low Bias | 0.593 |
Yes | 0.140 | 0.200 | -0.060 | High Bias | 0.064 | 0.063 | 0.001 | Low Bias | 0.761 | |
Fully Specified Regression Models | No | 0.138 | 0.200 | -0.062 | High Bias | 0.064 | 0.063 | 0.001 | Low Bias | 0.752 |
w/ Treatment-Covariate Interactions | Yes | |||||||||
Note: When pre-test scores are available, they are used as a covariate in the analysis model. In addition, we used pre-test scores to impute values and create weights. Bias estimates were computed as described in Chapter 4 and repeated at the beginning of this appendix. The level of the bias is characterized as "High Bias" or "Low Bias" based on the criteria established in Chapter 4. 90% CI refers to the 90-percent confidence interval around the impact estimate. For more details on the simulations, see Chapter 4 and Appendix C. |