Question

A power company wants to inspect a sample of 10 power poles in the field for quality control
purposes. There are 200 sequentially numbered poles out in the field. Use TWO possible
sampling methods that could be used to obtain the 10 pole sample; explain how the sample is
to be taken using the sampling methods identified.

Answer 1

Since the 200 poles are sequentially numbered, two appropriate sampling methods will be Simple random sampling and Systematic sampling.

Simple Random Sampling- A simple random sampling is one in which each unit of the population has an equal chance of being selected in the sample. In the given problem, this method can be used either by using a random no. table or by the lottery method. The latter will consist in creating chits of numbers of poles written on piece of paper and get them thoroughly shuffled then selecting a chit randomly out of those 200 chits. Repeating this for 10 times will constitute the sample.

Systematic Sampling: This method consists in first choosing a number randomly which called the random start and then select every kth unit from it in the sample where k= N/n, N denoting the population size and n denoting the sample size. In this problem, first we will choose our random start then we will choose every 20th unit from it as our sampled unit, since, in this problem we have k= 200/10 = 20. Repeating this for 20 times will get our sample completed.