The insertion gain of a hearing aid is defined to be the difference between the sound pressure level at the eardrum with and without the hearing aid in place. These sound pressure measurements can be made by a probe microphone placed in the ear canal of a subject. An experiment was conducted to investigate how the insertion gain of a particular hearing aid was affected by the elevation of the noise stimulus. Data were collected on the insertion gain for a constant noise stimulus placed at the horizontal level of the ear of a subject, placed above the horizontal level, and placed below the horizontal level. The data are listed in DS 11.4.6. What conclusions can you draw from this data set?