Sampling error, however, is oversimplified when presented as a single number in reports that may include subgroups, poll-to-poll changes, lopsided margins and results measured on the difference.

The potential degree of this error in a particular poll is reflected in the margin of sampling error, a measurement of how closely the poll reflects the full population.

Some of the better-known statistical rules of thumb that a smart consumer might think apply in polls are more nuanced than they seem. In other words, as is so often the case in life, it’s complicated.

Selecting a random sample from a set is simple. But what about selecting a fair random sample from a set of unknown or indeterminate size? That’s where reservoir sampling comes in, and [Sam R… ...