A sampling method where every nth item in the population is selected for the sample

The sampling method where every nth item in the population is selected for the sample is called systematic sampling. Here are the steps to perform systematic sampling:

1. Define the Population: The first step in systematic sampling is to define the population from which you want to draw a sample. The population should be defined in terms of specific characteristics, such as age, gender, geographic location, etc.

2. Determine the Sample Size: The next step is to determine the size of the sample you want to draw from the population. This will depend on the level of precision you want in your results.

3. Assign a Number to Each Element in the Population: Each element in the population should be assigned a unique number. This can be done in any order, as long as each element has a unique number.

4. Calculate the Sampling Interval: The sampling interval is calculated by dividing the total population size by the desired sample size. This gives you the 'n' in 'every nth item'.

5. Select the First Element: The first element is selected randomly from the first 'n' elements of the population. For example, if your sampling interval is 5, you would select a random number between 1 and 5.

6. Select Every Nth Element: After the first element is selected, every nth element is selected until the desired sample size is reached. For example, if your first selected element was number 3 and your sampling interval is 5, you would then select elements 8, 13, 18, and so on.

7. Analyze the Sample: Once the sample has been selected, it can be analyzed to draw conclusions about the population.

This method is particularly useful when the population is large and spread out over a large geographic area. It ensures that the sample is spread out over the entire population and is therefore more likely to be representative.