Does the cost differential between the two systems modify the impact of the findings?
From the beginning of the test, the researchers were well aware that the lensed indirect system cost more than the parabolic. Therefore, study results which favored the lensed indirect system over the parabolic wouldn’t be meaningful unless they also proved a superiority sufficient to offset the added cost. In this particular installation (a building with no unusual installation problems for either type of fixture), the cost differential for installed fixtures was between $100 and $200 per workstation, depending on the methods used to calculate the cost. The 1990 study revealed that the parabolic workers were losing substantial amounts of productive work time each day due to lighting-related health problems. The following three examples give an indication of the financial impact of that lost time, assuming a conservative installed cost differential of $200 per workstation and an average work loss differential of ten minutes per day.