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Threats to Conclusion Validity. Threats to Conclusion Validity. Low statistical power Violated assumptions of statistical tests Fishing and the Error Rate problem Low reliability of measures Poor reliability of treatment implementation. Threats to Conclusion Validity.
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Threats to Conclusion Validity • Low statistical power • Violated assumptions of statistical tests • Fishing and the Error Rate problem • Low reliability of measures • Poor reliability of treatment implementation
Threats to Conclusion Validity • Random irrelevancies in the setting • Random heterogeneity of respondents
Improving Conclusion Validity:General Guidelines • Want good statistical power (> .8) • Want good reliability • Want good implementation
Improving Conclusion Validity:Specific Suggestions • Pretest and posttest on same scales • Match before or after random assignment (but not in place of random assignment) • Use covariates • Increase reliability, especially of dependent measures • Adjust raw scores for unreliability • Estimate desired effect magnitude in advance • Each person as own control • Present effect and standard error • Select homogeneous samples