The same poll of 1,021 US adults showed that 75% believe that development of nuclear weapons by Iran is also a critical threat to US vital interests in the next 10 years. The margin of error for this estimate is also ±4 percentage points. A member of the US House Committee on Appropriations is satisfied with 95% confidence, but she wants a smaller margin of error than ±4 percentage points to be able to distinguish which threat is more concerning to Americans. Which of the following modifications will achieve the smaller margin of error at 95% confidence? a. change the sampling method
b. decrease in sample size
c. increase in sample size