When is heat exchanged during the refrigeration cycle?
during the initial condensation and final expansion of the refrigerant.
during the initial expansion and final condensation of the refrigerant.
during the pumping of hot air into the expansion valve.
during compression and heating of the refrigerant into a super hot vapor.

The force acting on a beam was measured under the same operating conditions and a sample of 5 data points was collected. this process was repeated by 3 observers. the pooled standard deviations of these 3 data sets was 1.21. determine the true mean force using all pooled data (with a 95% probability). the result should look like this: true mean = mean +/- margin of error