Create a frequency plot for raster elevation values with in a polygon

[DavisTolman]

I have a lidar DEM model of the Houston area floodplain with polygons representing areas protected by levees.  I would like analyze the elevation within each levee by sampling the elevation values within the polygons and representing them as a histogram or frequency plot.  Ideally, the x axis would be binned elevation and the y axis would be the frequency (count).  

I've tried the Sample Tool from the spatial analyst toolset, but instead of obtaining the elevation values, I seem to be getting a number between 1 and 256 (...the display value?)

[DavisTolman]

Thanks, I'll calculate statistics and retry.

[DavisTolman]

I've tried calculating statistics for this DEM, but the layer properties still says that no statistics have been calculated.  Is there something wrong with my raster or am I missing something else. 

Below is what my Zonal Histogram table looks like.  Rather than showing the rows as feet (elevation), it shows a objectid column instead.  I'm pretty sure that the values within the polygons represent the elevation distribution for that polygon, but the units are not apparent.