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STEM Fair Experiment Post #14 - Variety is the Spice of Life

We love variety - in food, movies, clothing, friends, vacations and so on. Well, STEM Fair Experiments don't mind variety... as long as the variety is controlled and organized. We understand that it doesn't sound like fun - but think of it this way -

Let's pretend you went to a theater to watch a movie and while you were there everybody was standing around and then all of sudden the lights began to flicker and before you knew it... different movies began showing and just when you thought everything was okay you heard loud crunching noises; would that bother you?

Well, what if we told you that everybody standing around were on line to get into the theater; the lights flickering was an indication that the movie was about to begin; the variety of movies playing was simply the trailers of movies due to be released and the crunching was the sound of people eating popcorn. Does that sound more organized and controlled? It does to us. You have to think of your STEM Fair experiment in an organized and controlled manner. This doesn't mean you can't have fun... it just means that every action, every material, and every variable has a purpose and a time to shine - just not all at once.

In yesterday's post we discussed three types of variables: Independent, Dependent and Controlled. Today we are going to review the types of independent and dependent variables for a STEM Fair Experiment. This is a quick post... but a mighty one. The information from yesterday and today will help build and support your STEM Fair Experiment - particularly when you have to observe and record data.

As you can see from the chart above; there are two types of independent and dependent variables, they are:

1. Quantitative

2. Qualitative

Their names give away some clues about what type of variable they are.

1. Quantitative Variables

a. Definition of Quantitative Variable:

The root word of Quantitative is: quantity. So these variables always use a number; a weight, distance, amount, volume, number of repetitions.

b. Examples of Quantitative Variables:

Independent Quantitative Variable: You may change the amounts of water you give to the plants. Perhaps Plant A receives 1/4 cup, Plant B receives 1/2 cup, Plant C receives 1 cup.

Dependent Quantitative Variable: You measure the height of each plant receiving the water. For example the height of Plant A is 12"; Plant B is 14"; Plant C is 10" tall.

c. The Role of Quantitative Variables:

They offer a definitive and objective role in an experiment. Quantitative Variables are all about numbers and facts - not opinions.

2. Qualitative Variables

a. Definition of a Qualitative Variable:

The root word of Qualitative is: quality. These variables are usually shown by using words and recorded observations. Qualitative Variables are sometimes called Category (Categorical) Variables.

b. Examples of Qualitative Variable:

A Qualitative Variable is usually something that you can place into a category such as: gender, pain, eye color, difficulty, hair color, dog breed, age, location, taste and color.

Independent Quantitative Variable: You may decide to interview three groups of women and their opinion on the ease or difficulty of a task. However, you choose to divide the women into three different age categories. Group A is: Age 18-25; Group B is: Ages 26-35; Group C is: Ages 36-45.

Dependent Quantitative Variable: How the women choose to rank the difficulty of the task that you assign them.

c. The Role of Qualitative Variables:

Qualitative Variables can offer a different and descriptive observation. Sometimes you can organize this type of variable by ranking the variable. For example: Perhaps you're asking a group of people to tell you how easy or difficult it is to do a task. You may assign numbers to this scale:

  1. Very Easy

  2. Fairly Easy

  3. Slightly Easy

  4. Neither Easy or Difficult

  5. Slightly Difficult

  6. Fairly Difficult

  7. Very Difficult

All of the variables that we reviewed serve very unique purposes and perspectives. The Quantitative Variable focuses on facts - not feelings. Sometimes this information doesn't offer the entire picture and if you were to include only quantitative data your experiment could appear one note without variation. The Qualitative Variable does just the opposite and leans toward the feelings and captures a different set of information. If your experiment utilized only qualitative information you could run the risk of not providing objective information that brings dimension and depth to a project. You can't have an effective choir of all sopranos - you need altos, tenors, and bases to bring variation to the music. The same applies to a STEM experiment - you need both quantitative and qualitative information to present a well balanced and thorough presentation.


We want you to brainstorm types of quantitative and qualitative information. We offered you some suggestions above - try to expand on those ideas or develop ones of your own.

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