One of the reasons that it is difficult to evaluate the effectiveness of a new energy conservation program is that

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Without a randomly assigned control group, it is challenging to determine if any changes seen in energy consumption are a direct result of the program or due to other external factors. A control group would provide a basis for comparison and help to isolate the effect of the program. Evaluations may still be time-consuming and difficult to obtain a large sample size, but the lack of a control group is the most significant challenge to evaluating the effectiveness of a new energy conservation program.

One of the Reasons That It Is Difficult to Evaluate