Appendix

Reading time
  • H0 / H1 : the null hypothesis of no difference, and its alternative.
  • p-value : the probability of observing such a difference if H0 were true. If this probability is low, it casts doubt on H0.
  • Alpha risk : the risk of asserting a difference that does not exist. Determined in advance, often 5 %.
  • Beta Risk : risk of missing a real difference.
  • Power : 1 − beta, the probability of detecting a true difference.
  • Parametric Test : assumes a law; more powerful if the assumption holds.
  • Nonparametric test : does not assume any law; more robust.
  • Paired data : two sets of measurements taken on the same individuals.
  • Bilateral / unilateral : «different from» versus «greater than.» You decide on the meaning before looking at the data.
  • BOB / WOW : the best and worst pieces, selected to highlight the contrast.