The answer is "an unrepresentative sample".
Biased Sample, otherwise called the Unrepresentative Sample is viewed as a weak analogy.
This fallacy (a misstep, and a legitimate error is a slip-up in thinking) is framed when a man reaches a determination of a populace in light of a measure that is one-sided or biased.
The sample is biased or Unrepresentative somehow because of not having been picked arbitrarily from the population.