But when the question of the pumping apparatus, to be worked by hand, is contemplated the difficulties introduced become yet more insuperable.

In addition to sampling error, which is a statistical function of the polling technique, practical difficulties of conducting a survey can introduce error in the findings.

The practical difficulties of conducting any survey may also introduce other souces of error into the poll.

In addition, the practical difficulties of conducting any public opinion survey may introduce other sources of error into the poll.

The scope of the census makes the margin of sampling error insignificant, but the practical difficulties of conducting any enumeration can introduce other sources of error into the census.

The practical difficulties of conducting any survey may also introduce other sources of error.

In addition to sampling error, the practical difficulties of conducting any opinion survey may introduce error into the poll.

Since this was not a sample survey, there are no sampling errors; however, the practical difficulties of conducting a survey may introduce errors, commonly referred to as nonsampling errors.

In addition to sampling error, the practical difficulties of conducting any survey can introduce other sources of error into the poll.

Besides sampling error, the practical difficulties of poinion surveys may introduce other errors.