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The research and development department of an appliance company suspects the energy consumption required of their 18 cubic foot refrigerator can be reduced by a slight modification to the current motor. Thirty 18 cubic foot refrigerators were randomly selected from the company’s warehouse. The first 15 had their motors modified while the last 15 were left intact. The energy consumption (kilowatts) for a 24 hour period for each refrigerator was recorded and stored in the data frame Refrigerator. The refrigerators with the design modification are stored in the variable modelA and those without the design modification are stored in the variable modelB. Is there evidence that the design modification reduces the refrigerators’ average energy consumption?