Is an estimate of the common population variance σ2. it provides a estimate of σ2 when h0 is true, and tends to become when ha is true. is an estimate of the common population variance σ2. it provides a estimate of σ2 regardless of whether h0 is true or not.

6–43 a food department is kept at 2128c by a refrigerator in an environment at 308c. the total heat gain to the food department is estimated to be 3300 kj/h and the heat rejection in the condenser is 4800 kj/h. determine the power input to the compressor, in kw and the cop of the refrigerator.