Skip to main content

TUTORIAL



This brief tutorial describes four examples of how a Randomizer form can be used to carry out common research tasks such as drawing a random sample of individuals from a population.

The full tutorial takes about 10 minutes to complete.

top of arrow graphic>

LESSON 2 OF 4

Random Assignment of 40 Participants to 4 Conditions


Although people sometimes confuse random assignment with random sampling, the two are really quite different. With random sampling, the goal is to choose a representative set of cases from a larger population. With random assignment, the goal is usually to give all participants an equal chance of being assigned
to each experimental condition (regardless of how representative the participants are).

Suppose, for example, that you're a medical researcher testing doses
of a new drug, and you want to randomly assign 40 volunteers to 4
experimental conditions:


  • Condition 1 = Wonderdrug 5%
  • Condition 2 = Wonderdrug 10%
  • Condition 3 = Wonderdrug 15%
  • Condition 4 = Placebo

You would begin by giving each volunteer an identification number (Participant 001, 002, 003, etc.), and then use the Randomizer form to generate 1 set of 40 non-unique, unsorted numbers with a range from 1 to 4 (representing the
four conditions).

Help

In some cases, you may wish to generate more than one set of numbers at a time (e.g., when randomly assigning people to experimental conditions in a "blocked" research design). If you wish to generate multiple sets of random numbers, simply enter the number of sets you want, and Research Randomizer will display all sets in the results.

Help

Specify how many numbers you want Research Randomizer to generate in each set. For example, a request for 5 numbers might yield the following set of random numbers: 2, 17, 23, 42, 50.

Help

Specify the lowest and highest value of the numbers you want to generate. For example, a range of 1 up to 50 would only generate random numbers between 1 and 50 (e.g., 2, 17, 23, 42, 50). Enter the lowest number you want in the "From" field and the highest number you want in the "To" field.

Help

Selecting "Yes" means that any particular number will appear only once in a given set (e.g., 2, 17, 23, 42, 50). Selecting "No" means that numbers may repeat within a given set (e.g., 2, 17, 17, 42, 50).
Please note: Numbers will remain unique only within a single set, not across multiple sets. If you request multiple sets, any particular number in Set 1 may still show up again in Set 2.

Help

Sorting your numbers can be helpful if you are performing random sampling, but it is not desirable if you are performing random assignment. To learn more about the difference between random sampling and random assignment, please see the Research Randomizer Quick Tutorial.

Help

Place Markers let you know where in the sequence a particular random number falls (by marking it with a small number immediately to the left).
Examples:

With Place Markers Off, your results will look something like this:
Set #1: 2, 17, 23, 42, 50
Set #2: 5, 3, 42, 18, 20
This is the default layout Research Randomizer uses.

With Place Markers Within, your results will look something like this:
Set #1: p1=2, p2=17, p3=23, p4=42, p5=50
Set #2: p1=5, p2=3, p3=42, p4=18, p5=20
This layout allows you to know instantly that the number 23 is the third number in Set #1, whereas the number 18 is the fourth number in Set #2. Notice that with this option, the Place Markers begin again at p1 in each set.

With Place Markers Across, your results will look something like this:
Set #1: p1=2, p2=17, p3=23, p4=42, p5=50
Set #2: p6=5, p7=3, p8=42, p9=18, p10=20
This layout allows you to know that 23 is the third number in the sequence, and 18 is the ninth number over both sets. As discussed in the Quick Tutorial, this option is especially helpful for doing random assignment by blocks.





← Lesson 1
Lesson 3 →