# Dictionary:Percent frequency effect (PFE)

**1**. The basic polarization parameter measured in frequency-domain resistivity surveys, being the percent difference in apparent resistivity measured at two frequencies:

where and are the low- and high-frequency apparent resistivities.

**2. Decade-normalized** ** PFE** is multiplied by the log of the frequency ratio:

**3**. Keller suggests that *PFE* be defined as:

where ρ_{1} and ρ_{2} are apparent resistivities measured at two frequencies that are a factor of 10 apart.