Multiple tests

Guidelines for empirical studies

• Researchers often perform many tests on the same data set

  • With many tests some ìsignificantî results will occur by chance

    • 20 tests at p=0.05, 1 spurious significant result almost certain
  • Need to adjust significance levels when performing multiple tests

    • Bonferroni adjustment

      • 10 tests, for 0.05 overall, 0.005 for individual tests

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