Final answer:
A decrease in aggregate demand will likely have a greater effect on inflation than on real GDP when the economy is at potential output, evidenced by a vertical aggregate supply curve at this level.
Step-by-step explanation:
A decrease in aggregate demand (AD) would be expected to have a bigger effect on inflation than real GDP under conditions where the economy is at or very close to its potential output. At this level, the aggregate supply (AS) curve is vertical, which means that any shift in AD will primarily affect the price level rather than output. High-interest rates, a decrease in government spending, or increased demand for cheaper imports can all lead to a decrease in AD, which might be expected to reduce inflation more than it would affect real GDP under these conditions.