Using this procedure each element in the population has a known and equal probability of selection (also known as epsem).
The researcher must ensure that the chosen sampling interval does not hide a pattern.
Example: Suppose a supermarket wants to study buying habits of their customers, then using systematic sampling they can choose every 10th or 15th customer entering the supermarket and conduct the study on this sample.
From the sampling frame, a starting point is chosen at random, and choices thereafter are at regular intervals.
To illustrate the danger of systematic skip concealing a pattern, suppose we were to sample a planned neighborhood where each street has ten houses on each block.
In this case, rather than simply counting through elements of the population and selecting every kth unit, we allocate each element a space along a number line according to its selection probability.
We then generate a random start from a uniform distribution between 0 and 1, and move along the number line in steps of 1.