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Biostatistics & Research · single question

Which statement about p-values is TRUE?

  1. It is the probability that the observed (or more extreme) data arose by chance, assuming the null is true
  2. It is the square root of the variance
  3. It is the chance the observed effect proves the null hypothesis false
  4. It is the probability of a Type I error (alpha)
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Correct answer: A. It is the probability that the observed (or more extreme) data arose by chance, assuming the null is true

  • A. Correct. The p-value is the probability of obtaining results at least as extreme as observed IF the null hypothesis were true.
  • B. Incorrect. The square root of the variance is the standard deviation, unrelated to the p-value.
  • C. Incorrect. The p-value does not 'prove' the null false; it quantifies evidence against it.
  • D. Incorrect. Alpha (the pre-set significance threshold/Type I error rate) is set by the investigator; the p-value is computed from the data and compared to alpha.

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