The research error described above is an example of selection bias.
Selection bias takes place when, from a population of interest, a group of individuals is selected in order to construct a sample but without a proper randomization. The result is a sample which is not representative of the underlying population.
According to the example, the target population of the research comprises all students but the sample only includes boys. Hence, selection has not been random because it followed a gender criteria, and the results obtained using it cannot be applicable to the whole population because they are affected by a selection bias.
In order to design her experiment, Phyllis will need:
- READING, as she will have to investigate the names of several fabrics (such as cotton, silk, linen, wool, cahsmere, leather, etc). She will also learn about waterproof materials.
- OBSERVATION as she performs the experiment. Because she will see that not every fabric repels water in the same way.
His approval rating was increased
