Sampling error and selection bias (cont.)

Selection bias

Selection bias is another reason why the statistics derived from our sample may be different to the true population value. Selection bias is introduced to our study when some members of the study population have a greater chance of being selected than others. If those who are selected differ in some way from those who are not selected, this may bias our results.

Unlike sampling error, selection bias is a type of systematic error. This means that if multiple samples were taken, the resulting values would be consistently higher or lower than the true population value, depending on the direction of the bias.