in statistics,

sampling biasis a bias in which a sample is collected in such a way that some members of the intended populationto be included than others.are less likely

The word bias could mean:

__in sampling__: give preference to selecting some individuals over others__in statistic__: certain responses are more likely to occur in the sample than in the population (statistic is the numerical summary of a sample)

Sources of bias:

- Sampling bias
- Nonresponse bias
- Response bias

**Sampling bias** means that the technique used to obtain the sample’s individuals __tends to favor one part of the population over another__. Sampling bias also results due to ** under-coverage**, which occurs when the proportion of one segment of the population is lower in a sample than it is in the population.

** Nonresponse bias** exists when individuals selected to be in the sample who do not respond to the survey have different opinions from those who do.

** Response bias** exists when the answers on a survey do not reflect the true feelings of the respondent.

** Nonsampling errors** result from data-entry error, undercoverage, nonresponse bias, response bias. Such errors could also be present in a complete census of the population. Sampling error results from using a sample to estimate information about a population. This type of error occurs because a sample gives incomplete information about a population.