Weaken an Argument Practice Test

A public health department concludes that a new advertising campaign caused a recent increase in flu vaccinations. The department notes that in the month after the campaign began, the number of vaccinations administered at local clinics rose by 15% compared with the previous month. The department therefore plans to run the same campaign every year to raise vaccination rates. Which of the following, if true, most weakens the argument?

A museum director argues that extending the museum’s hours to include Friday evenings will increase annual attendance. The director cites a three-month trial in which Friday-evening attendance averaged 400 visitors per night, and notes that the museum’s daytime attendance did not decline during the trial. The director concludes that making Friday-evening hours permanent will add those visitors to the annual total and will therefore increase ticket revenue. Which of the following, if true, most weakens the argument?