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Simple Random Sampling

When each eligible subject has the same probability of being selected for inclusion in your sample, it is called ‘simple random sampling.’ 

For example, suppose a school administrator over 4 schools wishes to find out students’ opinions about food served in the school cafeterias.  (S)he has a complete list of all students in the schools and decides to randomly select 150 students from the list. 

In this example, each student throughout the 4 schools has an equal probability of selection to be given the survey; therefore, it is a simple random sample.

As the name implies, selecting a simple random sample is, well… simple!

Here are the steps:

  1. Assign each member of your population a numerical label.
  2. Use statistical software or a random digit table to select numerical labels at random

Example:

A small catering business serves 9 reception centers. The owner wants to interview a sample of 4 clients in detail to find ways to improve services to his/her clients.  To avoid bias, the owner chooses a simple random sample of size 4. 

Step 1: 
Each reception center is assigned a numerical label 1-9.

1 - Darlene’s Wedding Center
2 - Magic Moments Reception Hall
3 - Rustic Realm Weddings
4 - Romance Gardens
5 - Classic Weddings
6 - Old Time Chapel
7 - Lovers Lane Weddings
8 - Accents-Modern Weddings
9 - Century Falls Reception Center

Step 2:
The owner decides to use a statistical software program to generate 4 numerical labels between 1 and 9 at random.  The software returns the following numbers:

5, 8, 6, 4

Therefore, the simple random sample to be interviewed in detail will be:

  • Classic Weddings (5)
  • Accents-Modern Weddings (8)
  • Old Time Chapel (6)
  • Romance Gardens (4)

 

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rev. 14-Aug-2012

 

 

 

Assign Numbers, Auto-Generate Random Selections
Resource Library

Statistical Links
Links to a variety of online statistical resources.

NEDARC Can Help

Contact a NEDARC statistician for help with simple random sampling.

 

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