A municipal corporation printed on the back of each property tax receipt a form asking the assessee to rate the corporation's services and to post the form to the head office. Of the 1,900 forms returned, four in every five rated the services poor, and the corporation's report concludes that four in every five of the city's assessees find its services poor. The report's reasoning is most open to criticism because

Nobody drew the 1,900; they drew themselves, and the act of drawing oneself is not evenly distributed. A householder with a grievance will find the stamp and the postbox, while a householder with nothing to complain of throws the receipt into a drawer, so the returned forms are a portrait of the discontented and not of the city. The share among the 1,900 may therefore stand far above the share among the assessees, and the report has no way of knowing by how much. What the services cost bears on whether the complaints are justified; where the forms were posted from is a detail of the post; and the third option attacks a claim the report never makes, since a rating of the corporation's services requires no assessee to receive every one of them.