Systematic Random Sampling

This method  is generally used in such cases where a complete list of the population is available from which sample has to be selected.

Under this method the kth item  is picked up from the sample frame and k is the sampling interval which is equal to number in:

K = Size or Number in Universe (N) /Proposed Size for a sample

Thus if 200 item are to be selected from a universe of 2,000  items the k will be 10.Now if the   starting number is say 3 the kth numbers will be 13^th , 23^rd ,43^rd,53^rd ,etc. As such it is necessary to select the starting point  carefully either by drawing a card from a well shuffled   pack of cards or by throwing a dice or by taking out a numbers chit from a lot of 1 to 10 numbers etc.

The method although called a systematic random sampling is not necessarily a very scientific   method .it is suitable when there is not much dispersion in the l universe. For example if in a housing colony very 10th house is a corner plot which is larger then. The first and if every 10^th house is taken starting with 1, it will give a biased selection. Similarly, kth telephone   number may have some speciality. Therefore, care should be taken to see that the systematic does not introduce any personal prejudice keeping in view the purpose of the inquiry.