The mailing went out on April 22, 2021. An unrelated ICRC “door-drop” campaign followed around May 25, and a TV spot ran in German-speaking Switzerland in the same period. This triggered the preregistration’s Case I contingency: the narrow window (gifts through May 31) is the principal sample for hypothesis tests, with the broad three-month window as descriptive robustness. The narrow flag keeps all letters and simply does not count gifts arriving after May 31.
AI -- please make this language less AI sounding, and explain it more fully. Use tooltips for details