Errors: What are they and how significant are they?

Errors in educational research and measurement arise from four main sources: (a) errors associated with the characteristic being measured – intrinsic errors, (b) errors arising from the instrument being used – instrumental errors, (c) errors involved in the act of measurement – observational errors. In addition, since it is rarely possible to take measurements of a complete population there are (d) errors arising from the process of sampling – sampling errors. Sampling errors are of two types. First, there are errors arising from a sample not being fully representative of the population from which it is drawn-sample bias. Secondly, there are errors that arise from the variability among the cases included in the sample, which can be estimated from information on the variability between cases and the number of cases-standard errors of sampling. Estimates of the standard error of sampling permit inferences to be drawn about the range of a characteristic in the population. The word “error ” has many meanings. The most common meaning is concerned with the idea of a “mistake ” which does not apply in this context. A further meaning is concerned with “the difference between an observed or estimated numerical result and the true or exact one”. However