Most experiments usually only have one independent variable and one dependent variable, but they will all have multiple constant variables. For example, in Experiment 2 above, some of the constant variables would be the type of plant being grown, the amount of fertilizer each plant is given, the amount of water each plant is given, when each plant is given fertilizer and water, the amount of sunlight the plants receive, the size of the container each plant is grown in, and more.
The scientist is changing the type of fertilizer each plant gets which in turn changes how much each plant grows, but every other part of the experiment stays the same. In experiments, you have to test one independent variable at a time in order to accurately understand how it impacts the dependent variable.
Constant variables are important because they ensure that the dependent variable is changing because, and only because, of the independent variable so you can accurately measure the relationship between the dependent and independent variables.
If you didn't have any constant variables, you wouldn't be able to tell if the independent variable was what was really affecting the dependent variable. For example, in the example above, if there were no constants and you used different amounts of water, different types of plants, different amounts of fertilizer and put the plants in windows that got different amounts of sun, you wouldn't be able to say how fertilizer type affected plant growth because there would be so many other factors potentially affecting how the plants grew.
If you're still having a hard time understanding the relationship between independent and dependent variable, it might help to see them in action. Here are three experiments you can try at home.
One simple way to explore independent and dependent variables is to construct a biology experiment with seeds. Try growing some sunflowers and see how different factors affect their growth. For example, say you have ten sunflower seedlings, and you decide to give each a different amount of water each day to see if that affects their growth.
The independent variable here would be the amount of water you give the plants, and the dependent variable is how tall the sunflowers grow. Explore a wide range of chemical reactions with this chemistry kit. Build and test a range of simple and complex machines with this K'nex kit.
How does increasing a vehicle's mass affect its velocity? Can you lift more with a fixed or movable pulley? Can you identify the independent and dependent variables for each of the four scenarios below? The answers are at the bottom of the guide for you to check your work. Scenario 1: You buy your dog multiple brands of food to see which one is her favorite.
Scenario 2: Your friends invite you to a party, and you decide to attend, but you're worried that staying out too long will affect how well you do on your geometry test tomorrow morning. Scenario 3: Your dentist appointment will take 30 minutes from start to finish, but that doesn't include waiting in the lounge before you're called in.
The total amount of time you spend in the dentist's office is the amount of time you wait before your appointment, plus the 30 minutes of the actual appointment. Scenario 4: You regularly babysit your little cousin who always throws a tantrum when he's asked to eat his vegetables.
Over the course of the week, you ask him to eat vegetables four times. Knowing the independent variable definition and dependent variable definition is key to understanding how experiments work.
The independent variable is what you change, and the dependent variable is what changes as a result of that. When graphing these variables, the independent variable should go on the x-axis the horizontal axis , and the dependent variable goes on the y-axis vertical axis.
Constant variables are also important to understand. Previous Section Next Section. Finding and Using Health Statistics Glossary.
Content Dependent and Independent Variables In analytical health research there are generally two types of variables. Due to a long history of unethical research in health and social sciences, researchers have many ethical obligations when conducting research, particularly with human subjects.
These obligations were first codified in the Nuremburg Code in , which specified that the benefits of research must outweigh the foreseeable risks. Ethical obligations continue to evolve to protect human subjects, including confidentiality and anonymity unless waived and informed consent.
An easy way to remember is to insert the names of the two variables you are using in this sentence in they way that makes the most sense. Then you can figure out which is the independent variable and which is the dependent variable:.
Independent variable causes a change in Dependent Variable and it isn't possible that Dependent Variable could cause a change in Independent Variable. We see that "Time Spent Studying" must be the independent variable and "Test Score" must be the dependent variable because the sentence doesn't make sense the other way around.
Fun Graphing Exercise! What are Independent and Dependent Variables? Ever wonder what your personality type means? Sign up to find out more in our Healthy Mind newsletter. National Library of Medicine. Dependent and independent variables. Steingrimsdottir HS, Arntzen E.
On the utility of within-participant research design when working with patients with neurocognitive disorders. Clin Interv Aging. Kaliyadan F, Kulkarni V. Types of variables, descriptive statistics, and sample size. Indian Dermatol Online J. Independent, dependent, and other variables in healthcare and chaplaincy research. J Health Care Chaplain. Weiten W. Psychology: Themes and Variations. Cengage Learning; Experimental Psychology. Your Privacy Rights.
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