If you're comparing technologies, then you want to eliminate the variable of condition.
If you are comparing the values or efficiency of actual old fridges and new fridges - for example, to decide whether to replace the old ones - then it's false data to assume the old fridges are in the same condition as new ones.
If you're comparing technologies, then you want to eliminate the variable of condition.
If you are comparing the values or efficiency of actual old fridges and new fridges - for example, to decide whether to replace the old ones - then it's false data to assume the old fridges are in the same condition as new ones.