How can systematic sampling be biased?
There is a possibility for bias to emerge in systematic sampling, if the researcher throws the randomness into air and uses his own discretion in selection of items in framing the sample.
Under Systematic sampling - the enumerator has to prepare the list of items in the population, First, he will have to select the first item at random, Then he will select the every nth item.
For example: Let us assume there are 200 students in a school. Of which 10 are to be selected. The bias will arise like this.
The researcher will select the 7th item purposely. From then on he decides to choose every 10th student in the list. The 17th, 27th 37th ........ students are his own choice. He pre-arranged the list for these students to get selected..