A plan to reduce energy usage proposes that if households switch to LED lighting, the national energy bill will drop by 20% within a year. The plan assumes savings from one program will extrapolate nationally without accounting for variations in household size and usage. Which of the following, if true, identifies a flaw in the plan?

• A. The plan ignores regional differences in energy usage across households.
• B. The plan uses LED lighting, which is more expensive upfront but cheaper long-term.
• C. The plan would require government subsidies to be effective.
• D. The plan relies on a private study with a small sample.

Answer: (A)

The main idea being tested is that you can’t reliably project a result from one program onto an entire population without accounting for variation among households. Different homes vary in size, how many people live there, and how much electricity they use for lighting versus other needs. Some places use more energy for heating or cooling, where lighting improvements won’t affect the bill as much. If you assume every household would see the same 20% drop, you’re ignoring these differences, so the national savings are likely overestimated or misestimated.

That’s why the option pointing out regional differences in energy usage across households identifies the flaw: it directly highlights the mismatch between a uniform national claim and the real variability in how people actually use energy. The other options don’t address this extrapolation issue as directly. For example, cost upfront versus long-term savings or the need for subsidies don’t speak to whether the projected national impact should be uniform, and a small-sample study raises reliability questions but not the specific problem of assuming identical savings across diverse households.