n = Sample size. Procedure for selection of samples by systematic sampling method (i) If we want to select a sample of students from a class of students, the sampling interval is calculated as k N . Thus sampling interval = denotes that for every samples one sample has to be selected. (ii) The firstsample is selected from the first (sampling interval) samples through random selection procedures.
XII Std - Business Maths & Stat EM Chapter - - Sampling Techniques and Statistical Inference (iii) If the selected first random sample is , then the rest of the samples are automatically selected by incrementing the value of the sampling interval ( k = ) i.e., , , , , , , , , , . Example: Suppose we have to select items out of , . The procedure is to number all the , items from to , . The sampling interval is calculated as k N .
Thus sampling interval = denotes that for every samples one sample has to be selected. The first sample is selected from the first (sampling interval) samples through random selection procedures. If the selected first random sample is , then the rest of the samples are automatically selected by incrementing the value of the sampling interval ( k = ) ie, , , , , , , , , , , , , , , , , , , , . Items bearing those numbers will be selected as samples from the population.
Merits . This is simple and convenient method. . This method distributes the sample more evenly over the entire listed population.
. The time and work is reduced much. Demerits . Systematic samples are not random samples.
. If N is not a multiple of n , then the sampling interval ( k ) cannot be an integer, thus sample selection becomes difficult. . .
Sampling and Non-Sampling Errors: A sample is a part of the whole population. A sample drawn from the population depends upon chance and as