Sampling Errors

Systematic Errors (Non-Sampling Errors) Systematic errors result from decisions that bias the sample selection or response to your survey

• Population Specification Error: This error is one of not understanding who you should be surveying
• Sample Frame Error: A frame error occurs when the wrong sub-population is specified from which the sample is drawn
• Selection Error: Selection error results when the respondents self select their participation - those that are interested respond
• Non-Response: Non-response errors occur when non-respondents are different than those who respond.

Non-Systematic Errors (Sampling Errors)
Sampling errors occur because of variation in the number or representativeness of the sample that responds. Sampling errors can be controlled by

• Careful sample designs
• Large samples
• Multiple contacts to assure representative response.

Two types of samples may be drawn: a probability sample where every person in the sample has an equal and known probability of being selected, and a non-probability sample where the probability of a person being selected is unknown.