sampling error 
noun [mass noun] Statistics
Error in a statistical analysis arising from the unrepresentativeness of the sample taken: a percentage of the total variation is attributable to sampling error...
- This is because the statistical sampling error of the phase is inversely related to the squared coherence.
- A search for moderators was pursued only if less than 60% of the variation of observed coefficients could be explained by a combination of sampling error and measurement error.
- In addition to these caveats, sampling error due to analysis of an inadequate sample volume can also lead to a false-negative test result.