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Study Analysis Plan

Lead Author(s): Jeff Martin, MD

When Written

Written before the data are analyzed

Study Analysis Plan Content

  • Detailed description of the techniques to be used to analyze data, step by step
  • Forms the basis of Statistical Analysis section in manuscripts
  • Parameters/rules/logic to guide key decisions:
    • Which variables will be assessed for confounding and interaction?
    • What p value will be used to guide reporting of interaction?
    • What is a meaningful difference between two estimates (e.g., 10%) to determine confounding?
For example, it will outline whether you will use a forward or backward selection process.
  • It will state which p value thresholds you will use to decide whether to report interaction or not.
  • It will also state the rules you will use to deal with the bias-variance tradeoff of determining what to control for.
  • It will contain how you define a meaningful difference between two estimates (e.g., crude and adjusted) to determine confounding.

Required

Required for clinical trial registration
  • Can observational work be far behind?
Such a pre-specificed plan is required for registration of clinical trials with the FDA. I have to wonder if observational studies are far behind?

Utility

A plan helps to keep the analysis:
  • Focused
  • Reproducible
  • Honest (avoids p value shopping)
There are many advantages to having such a plan.
  • For one, it helps keep you focused in your own work and avoids your wasting a lot of time making things up as you go.
  • A well written plan is also one that is reproducible by others.
  • Finally, as I mentioned above, a plan helps keep you honest by avoiding p value shopping, by which I mean trying a number of different approaches until you get the answer you like.


Topic revision: r2 - 03 Jun 2009 - 15:16:33 - MaryB?
 

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