False-positive rate with no true difference (8 per group, 100,000 experiments, seed 20261110):
  two_sided                                               0.0477
  one_sided_direction_fixed_in_advance                    0.0484
  switch_to_one_sided_if_it_helps                         0.0968
  one_sided_planned_but_wrong_direction_also_reported     0.0718
  one_sided_at_0.025                                      0.0242
Animals per group, two-sample Student t-test, alpha 0.05:
  power 0.80 d 0.5: two-sided  64  one-sided  51  saving 20.3%
  power 0.80 d 0.8: two-sided  26  one-sided  21  saving 19.2%
  power 0.80 d 1.0: two-sided  17  one-sided  14  saving 17.6%
  power 0.80 d 1.5: two-sided   9  one-sided   7  saving 22.2%
  power 0.80 d 2.0: two-sided   6  one-sided   4  saving 33.3%
  power 0.90 d 0.5: two-sided  86  one-sided  70  saving 18.6%
  power 0.90 d 0.8: two-sided  34  one-sided  28  saving 17.6%
  power 0.90 d 1.0: two-sided  23  one-sided  18  saving 21.7%
  power 0.90 d 1.5: two-sided  11  one-sided   9  saving 18.2%
  power 0.90 d 2.0: two-sided   7  one-sided   6  saving 14.3%