Sample bias Design systematically favors certain outcomes. Chance error Error due to the variability of samples. Sample bias is the result of a poor sampling plan. Very often the surveyor tries to get a representative sample which is an extremely poor approach. Sample bias can be eliminated using a proper sampling plan.
Chance error is due to variability of samples taken.
Chance error can not be eliminated but it can be made small. A stratified sampling approach is used. Break the population into strata and substrata determined by by a combination of geographical and demographic considerations. Randomly select strata and substrata for sampling Stratified sampling size Can usually get pretty accurate results using a sample of around 1500. Factor A factor is any of the explanatory variables in the experiment.