  The mean pulsation period of ZZ Ceti stars increases with decreasing
effective temperature as we traverse from the blue to the red edge of the
instability strip. This well-established correlation between the mean period
and spectroscopic temperature suggests that the mean period could be utilized
as a tool to measure the relative temperature of the star independent of
spectroscopy. Measuring the pulsation periods of a ZZ Ceti star is a simple,
model-independent, and straight forward process as opposed to a spectroscopic
determination of its temperature.
  Internal uncertainties in determining the spectroscopic temperature of a ZZ
Ceti star are at least 200K, 15% of the 1350K width of the instability strip.
The uncertainties in determining the mean period arise mostly from amplitude
modulation in the pulsation spectrum and are smaller than 100s for 91% of the
ZZ Ceti stars, <8% of the 1300s width of the instability strip. In principle
this implies that for 90% of the ZZ Ceti stars, the average uncertainty in
determining the location of a ZZ Ceti star within the instability strip
decreases by a factor of two in utilizing the mean period of the ZZ Ceti star
as a temperature indicator rather than conventional spectroscopy. Presently we
only claim that the relative temperatures of ZZ Ceti stars derived by using the
mean pulsation period are certainly as good as and perhaps about 15% better
than spectroscopy.
