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Série Temporal em Estudos de Saúde Pública

Série Temporal em Estudos de Saúde Pública. Clarice Amorim e Jessica Johnson. Interrupted Time-Series. Clarice Amorim & Jessica Johnson. Overview. Overview of Interrupted Time-Series (ITS) Types of Designs Validity Threats Statistical Techniques The Debate

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Série Temporal em Estudos de Saúde Pública

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  1. Série Temporal em Estudos de Saúde Pública Clarice Amorim e Jessica Johnson

  2. Interrupted Time-Series Clarice Amorim & Jessica Johnson

  3. Overview • Overview of Interrupted Time-Series (ITS) • Types of Designs • Validity Threats • Statistical Techniques • The Debate • Applying ITS to the “real world”

  4. What is Interrupted Time-Series? (ITS) “Large series of observations made on the same variable consecutively over time” (Shadish, Cook, & Campbell) • The key in ITS designs is knowing exactly when the independent variable was manipulated, or when the intervention was introduced. • Repeated measurements allow us to identify patterns of change: manipulating the independent variable (introducing an intervention) should cause changes in the level and/or slope of the regression line. • ITS designs can also demonstrate variability over time (continuous or discontinuous effects, immediate or delayed effects).

  5. Source: http://xkcd.com/418/

  6. Types of ITS designs • Two basic types of multiple baseline designs (MBDs): • One outcome measured across several cases at different points in time. • Several outcomes measured on one case, the intervention applied to one outcome at a time. • Assumptions? • Advantages? • Disadvantages?

  7. Types of ITS designs O1 O2 O3 O4 O5X O6 O7 O8 O9 O10 O1 O2 O3 O4X O5 O6 O7 O8 O9X O10 O11 O12 O1 O2 O3 O4X1 O5 O6 O7 O8 O9 X2 O10 O11 O12

  8. Major validity threats • Internal Validity • History • Instrumentation • Selection • Statistical Conclusion Validity • Construct Validity • External Validity http://xkcd.com/605

  9. Statistical Techniques for ITS Autocorrelation

  10. Statistical Techniques for ITS • ARIMA modeling • C-test • ITS Experiment method • ITSACORR • Latent Growth Modeling • Meta-Analysis

  11. Is the interrupted time series an experiment? a debate

  12. Summary of the debate • Calling ITS an experiment does not equate it to RCT • Power of nomenclature • Depends on the purpose of your study

  13. Systematic Replication “It might be objected that in community intervention research, one is testing complex, multi-faceted interventions, often involving a series of efforts, and that it will be difficult to sort out which activities contributed to any changes that are observed. […] Practical experience suggests, however, that one emerges from the first effort with a good deal of clarity about how to streamline the intervention” (Biglan 2000:40)

  14. Article Reading “Effect of pay for performance on the management and outcomes of hypertension in the United Kingdom: interrupted time series study”

  15. Article Discussion Questions What are some of the threats to validity? How would you improve the study? What are the implications of these “null” findings?

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