1.4 Random sampling
To take a random sample, you need to start by giving every item in the population a unique identifier, usually a number from 1 to n where n is the total number of items. The population of the village with which you have been working is 1500 residents so n = 1500. Then using some kind of independent method of random selection, such as a random number table or button on a calculator, select items (residents) until the required sample size is reached. If the same item is chosen more than once, simply ignore the repeated selection and choose again.
Watch the following video to learn how to use a random number table to take a random sample of the village population.
As you will have seen towards the end of the video, there were also some ideas that could be used for taking a random sample in the classroom.
Activity 3 Random sampling on a calculator
Watch this video about how to use a random number generator on a calculator and in a spreadsheet to create a random sample. Then attempt the activities that follow the video.
Please note our example generates random numbers between 0 and 1 with up to 3 digits. Other calculators may produce random numbers of varying precision.
Use two different random number generators to take a sample of size 12 from a population of size 1500. Write down the unique identifiers for the items (people) selected in the two samples you take.
If you have a different calculator to the one used in the video, perform an internet search for how to use the random number generator function on your calculator.
Reflect:
Is there any pattern or similarity in the samples?
Did you have any problems in taking the samples? If so, did you overcome them and how?
Do you have a preference as to which random number generator is better? Why?