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Statistics LibreTexts

1.5: Sampling Demonstration

  • Page ID
    267
  • Learning Objectives

    • Distinguish between simple random sampling and stratified sampling.
    • Describe how often random and stratified sampling give exactly the same result.

    Instructions

    The sampling simulation uses a population of \(100\) animals: \(60\) lions, \(30\) turtles, \(10\) rabbits.

    Options

    sampling_demo_randomsample_pic.png: This option allows you to draw a sample of \(10\) animals at a time with each animal having an equal chance of being selected.

    sampling_demo_stratifiedsample_pic.png: This option allows you to draw a sample of \(10\) animals at a time, with each number of animals from a group being proportional to their group’s size of the population.

    Simulation Results

    GroupAnimals_Samplng_Demo.jpg
    Figure \(\PageIndex{1}\): Simulation Results

    The number of animals chosen from each group when a sample is drawn is shown next to the picture of the animal.

    When you give it a try

    Random Sampling

    • Begin by leaving the sampling_demo_randomsample_pic.png option selected.
    • Click on the sampling_demo_select10pic.pngbutton, \(10\) animals will be selected out of the population.

      Note: The animals become highlighted in blue and a number count of each animal selected will be listed by each animal image.

    • Each time you push the button, another sample will be drawn and the new tally will be shown on the right side of the previous sample.
    • You should get different tally results for each animal as you select , however the computer may give you the same number drawn from an animal category every now and then.

    Stratified Sample

    Note: Your animals should become highlighted in blue and a number count should be listed by each animal image.

    • Click on the sampling_demo_reset_pic.png button, to clear the simulation.
    • Select the sampling_demo_stratifiedsample_pic.pngoption.
    • Click on the button a few times.
    • As you get a new tally for every button, notice that the number of animals stays the same, but the animals selected are not always the same animals.

    Illustrated Instructions

    The opening screen of the sampling simulation displays all \(100\) animals in the population. You can select between a random sample and a stratified sample directly below the population and then generate a sample of ten animals.

    sampling_demo_start.jpg
    Figure \(\PageIndex{2}\): Sample Choices

    Below is an example of a random sample. Notice that animals selected are highlighted in the population and the total number of animals selected from each category is listed at the bottom of the simulation.

    sampling_demo_changed.jpg
    Figure \(\PageIndex{3}\): Random Sample

    Contributors

    • Online Statistics Education: A Multimedia Course of Study (http://onlinestatbook.com/). Project Leader: David M. Lane, Rice University.