What Systematic sample is
A systematic sample is a type of probability sample in which each sample unit has an equal probability of being selected. It is also known as a periodic sample. Systematic sampling is used when a sampling frame is available that lists all members of the population in an ordered fashion.
Steps for Systematic Sampling:
- Determine the sampling interval (n) which is the total population size divided by the desired sample size.
- Begin by selecting a random starting point in the population.
- Take every nth item from the sampling frame until the desired sample size has been reached.
- Record the sampled items and their corresponding population numbers.
- Using the recorded population numbers, select the corresponding items from the population.
Examples
-
A researcher wants to measure the satisfaction levels of customers at a particular restaurant. He obtains the list of all customers who have visited the restaurant in the past month and selects every 10th customer from the list to be included in the survey.
-
A marketing analyst is interested in understanding the effectiveness of a new advertising campaign. She obtains the list of all individuals who were exposed to the ad and selects every 20th individual from the list to be included in the survey.
-
A political science professor wants to measure public opinion of a certain policy. He obtains the list of all registered voters in the state and selects every 25th voter from the list to be included in the survey.