Final answer:
A census collects data from an entire population, while a sample is a subset used to represent the whole. A sample is biased when it does not accurately represent the population.
Step-by-step explanation:
In statistics, a census is a method of collecting data from an entire population, while a sample is a subset of the population used to represent the whole. A census aims to gather information about every individual or unit in the population, whereas a sample collects data from only a portion of the population.
A sample can be considered biased when it does not accurately represent the characteristics and diversity of the population. This bias can occur due to specific selection methods, such as convenience sampling or non-response bias, where certain groups are over or underrepresented. For example, if a survey is conducted only in a specific geographic area or at a certain time when certain groups are less likely to participate, the sample can be biased.