Teaching Independent Variables and Dependent Variables
Hi everyone, I am new to this site so please forgive me if I'm in the wrong spot. I just started my first week of teaching. I was wondering if anyone had any advice on teaching independent variables and dependent variables. I wanted to start out with an easy lab (posing a question-9th grade level) for students to understand themselves what independent and dependent variable is, control, and constants. Does anyone have any ideas how to start out this topic? Thank you!
Something I was thinking of doing was measuring the density of pennies (comparing pre-1982 to post-1982). This would also lead you into methods of measurement, since you would be using graduated cylinders.
This is much of a scientific question as it is a math question and the answer is not so black n white as we like to think it is.
The best way to teach it is to go to functions. What you plug in is independent. You can plug in any number you want. What you get out is dependent, you don't know what you're gonna get until you plug a number in.
The problem is the concept of being able to back calculate. I can say that I want Y to be something so what does X have to be to make that happen.
It's a challange to teach, but the bottom line is that X has be there first. X is the independent and Y responds to X. At the college or honors level, X and Y are what we choose them to be and they are interchangable.
In honesty, I don't teach this well. It is an extension of Einstien's theory of Relativity and that's a hard concept to get your mind around.....much less explain. However, sharing that detail with your students makes them want to go after it. They like the idea of grasping something that few comprehend.
Pose several situations that don't use the words depends, depend, dependent, etc, then get the students to change the wording to a statement that uses those words. For example:
A waitress makes $50 in tips on a day she serves 15 tables. Another day, she serves 25 tables and makes $100. The students would then write "The amount of money she makes depends on the number of tables served". Then have them label the part before the word "depends" as the dependent variable and the part after it as the independent. You might want to create a fill in the blank sheet for the first time you present it to them, then have them do in again without the aid. I find presenting students with a few dozen senarios helps them tremendously. They get comfortable with the terminology while looking at every day situations.
Some other examples I've used are: cost and profit, sales and profit, calories and weight, exercise and weight, study time and grades, hours spent babysitting and spending power, etc. The important thing is to make the situations directly relevant to their lives or something they have a basic understanding of already, so its not a stretch for them to see the connection.
__________________ The light at the end of the tunnel has been turned off due to budget cuts.
I was going to say something similar to mmswm actually.
I think it is important when teaching independent and dependent variables that the word "depends" is used, because for me it took a long time to get into my head which was dependent and which was independent, but once I realized the meaning behind the word, I could stop and think it all through. Makes it all SO much easier!
Great grandma depends on Depends.
In this case, great grandma is the dependent variable, and Depends are the independent variable
Another fun idea is "does your arm span depend on your height?" Then the students can measure their height/arm span in centimeters and practice creating a graph to see if a relationship exists.
I also do an experiment seeing how soap affects water tension. It involves counting the drops of water that fit on a penny. It's a good tie into detergent water pollution and how it affects animals like water striders. Also- the variables within the groups varies greatly- so it leads to good discussion about why the data varies.
This isn't an activity idea, but a mnemonic I use to help them remember how to graph is DRY MIX - the Dependent or Responding variable goes on the Y axis and the the Manipulated or Independent variable go on the X axis.
Our district started using the terms "manipulated" and "responding" about 10 years ago, and I explain it in two ways. First, I explain the the manipulated variable is what the scientist changes (or manipulates) and the responding variable is what changes in response. I also tell them that manipulated is in the past tense - responding is in the present - the scientist has to change something first, or in the past, to make a change happen in the present.
In addition to hands-on activities, i'll periodically give them sample experiements with sample data to graph. They have to figure out which is which. It helps!