Designing an Experiment: (The Scientific Method in Action part 1)
Lesson 6 of 9
Objective: Students follow the steps of the scientific method to design an experiment to test the effects that vertigo has on their ability to perform basic tasks.
This lesson sequence finally allows students to put the experimental design skills they’ve been practicing in a purely theoretical sense into practice.
Since this is very early in the year, I prefer that the first experiment not be dependent on too much content knowledge. The idea is to get students into the practice of actually doing science early enough that they understand the class won’t just be learning about science. Additionally, since this experiment can be conducted in 2-3 days, it’s a good way to actually demonstrate experimental error (which will be addressed after the lab report) and help fine-tune students’ sense of experimental design before they tackle the types of experiments in environmental science that unfold over longer time frames (e.g., an experiment to study the effects of nutrient deficiencies on plant growth can’t be conducted in 2-3 days).
Again the focus of this lesson sequence is on developing the skill of designing, conducting, and then documenting an experiment. In this case, we start with a phenomenon familiar to most every student: the sense of dizziness one gets after spinning around. This experiment asks students to examine how this sense of dizziness (physiologic vertigo) affects someone’s ability to perform basic physical and written tasks.
The advantages of an experiment built around this common phenomenon are threefold:
1. It’s immediately familiar (and somewhat mysterious) to most students.
2. It’s a lot of fun for the students (lots of laughing… yes science can be fun!)
3. It’s a great opportunity to get outside with your class and get them used to the idea that an environmental science class is going to use the “world” as a classroom.
Also, please note that this activity must be performed outside in a grassy area free of obstructions (or inside a gym if you have mats on the ground). Your students will fall down frequently… no need to get sued this early in the year. Make sure you get proper authorization from your principal before you begin this lesson sequence.
A few meters of yarn or string
Connection to Standard:
In this lesson, the connection to the standard isn’t so much in the fact that it’s a “research project” as described in the language of the standard itself. Rather, in a more scientific sense, it is very much a focused effort to solve a problem systematically. The question of narrowing or broadening the inquiry when appropriate comes up when students modify their experimental designs in response to questions of what kind of data they will collect, what specific variables they intend to study, what procedures help maintain control of the experiment, which factors remain constant, etc.
To begin, I tell students about the time I had to stop at a police checkpoint set up along the road on a Friday night. I tell them that the officer asked if I had been drinking (I said no), but that he then shined a light in my eyes and made me track his finger with my eyes while keeping my head still. I then ask students why the officer did this test rather than just take me at my word. They usually reply something like, “to see if you were drunk!”. After the laughter dies down, I’ll ask why police are concerned if people are drinking while driving and students will likely respond with the common knowledge of the dangers of impaired driving.
I then ask students what other field sobriety tests are common, answers will vary but commonly include “walking in a straight line, touching your fingertip to your nose, saying the alphabet backwards” and so on. I ask, again, why would officers use these tests to determine intoxication and students will likely respond that alcohol affects your balance and coordination, making it dangerous to operate a vehicle.
I then ask what other ways officers can determine, definitively, that someone has been drinking. Students will likely mention a "breathalyzer", an instrument to measure the concentration of alcohol in the blood. I then ask students what the blood alcohol concentration (BAC) limit is in California. After they respond with guesses, I project the DMV chart that shows the .08 BAC limit and the number of drinks it takes to reach that limit.
I then mention that some people believe that alcohol doesn’t affect everyone the same way, and that some people can be over the legal limit, but still be effectively “sober”. I ask students what they think, should someone with a BAC over the limit be considered safe to drive if they can perform the field sobriety checks with no problems? Should someone that can not perform the sobriety checks be considered unfit to drive even if their BAC is within the legal limts?
This should generate a short discussion where students are likely to express different opinions. I tend to let the discussion go for no more than a few minutes, but it could go much longer if you prefer.
I then tell students that we’re going to test the effects of being intoxicated, to see if it affects people in the same way, but no, we won’t be drinking alcohol.
(Please note, for those that would prefer not to discuss alcohol in class, you may begin the lesson from the following point. For my part, I am a high school teacher. I know that alcohol is an attention getter and students tend to be more invested in an experiment that models a real world problem than if the experiment is just, “let’s get dizzy and see what happens”. Again, take the approach you are most comfortable with, but I think it’s better to address alcohol than pretend it doesn’t exist.)
I ask students what some ways are to make yourself dizzy or lose your balance. Students will likely mention spinning around. I do a few turns in front of the class as an example and ask how many students have experienced that phenomenon… chances are that most students have. I explain that this loss of balance is caused by a disruption of normal equilibrium* (or balance) called physiologic vertigo, a sense that your environment is moving or spinning when you are still. I explain that we will be using spinning as a way to simulate the vertigo caused by intoxication.
By this point of the year, I have already arranged students into lab groups of 4 students, but you may prefer to allow them to choose their own lab groups. I tell students that their groups will be responsible for designing an experiment to answer the following question:
How does vertigo (a loss of equilibrium) affect someone’s ability to perform basic tasks?
I also provide the following sub-questions to guide their experimental design: Are the effects of vertigo predictable and consistent? In other words, does everyone that spins around get affected? If so, do they get affected equally?
I then distribute the instructions and allow groups to begin to design the experiment.
*If time allows, I might put the word “equilibrium” on the board along with “= lb” (hopefully they can guess that means “equal weight” or balance). This is a good opportunity for callback to the etymology lesson.
Designing the Experiment
After the warm up, students get into lab groups of 3-5 students and I remind them that we are attempting to answer the question, How does vertigo (a loss of equilibrium) affect someone’s ability to perform basic tasks?
I remind groups that they will need to first propose a hypothesis, or possible answer to the question, and then design tests to prove or disprove the hypothesis.
I then distribute the instructions (one sheet per group) and we quickly discuss the requirements of the experiment. I let students know that they will be testing their hypothesis about the effects of vertigo using at least 3 written tasks and at least 2 physical tasks.
As students begin to work and design their experiments, I go from group to group, looking for four things:
1. a testable hypothesis
2. a description of the procedures they will follow for each of their written and physical tasks
3. a description of the types of quantitative and qualitative data that will be collected from each task
4. a distinction between a control group and an experimental group
Before spending too much time with any one group, I try and make sure that, at a minimum, every group has proposed a testable hypothesis. The most basic hypothesis might be something as simple as, “vertigo makes someone worse at completing tasks”. More complex hypotheses may address sub-questions of consistency, intensity, duration, etc. (e.g., “The impairing effects of vertigo subside after a short time”, “physiologic vertigo impairs some but not all students’ ability to perform basic tasks”, “Vertigo impairs the ability to perform physical tasks but does not affect written tasks” etc).
Students will test their hypotheses by performing at least 3 written tasks and at least 2 physical tasks. I ask that they write down, step by step, the “rules” or procedures for each task, reminding them that not following a set procedure introduces additional variables into the experiment when the single variable should be whether or not they are experiencing vertigo while performing the task.
For the written tasks, I provide each group with one copy of the written tasks resource so they can plan how they will use it during the experiment (Before we actually conduct the experiment, I make enough double-sided copies for a ratio of one sheet per student… with a few extra as some students invariably decide they made a critical error that requires the written tasks to be started again).
This resource consists of simple mazes, puzzles, connect the dots, etc. It should be obvious to students that these written tasks are easy to perform under normal circumstances (which should be a good point of comparison and make the effects of vertigo readily apparent).
Each group decides their particular rules of completing the written tasks, but I have provided space to record the number of mistakes, and time for completion. When talking to individual groups, it helps to see if they remember that these would be examples of quantitative data. I also ask students what kinds of qualitative data they might be able to collect from the written tasks, and how that might be important in ultimately evaluating their hypothesis.
As for physical tasks, students are required to test at least 2 physical tasks of their choosing. If students are struggling to come up with physical tasks, I suggest some of the basic field sobriety tests (e.g., walking in a straight line, looking up with arms outstretched and touching the tip of each index finger to the tip of your nose, tracking a finger with your eyes without moving your head, etc.). However, students tend to be creative with physical tasks. In the past, students have come up with great ideas for physical tasks such as:
- repeatedly throwing a tennis ball in the air and trying to catch it
- running a zig-zag course around cones or spots on the ground
- doing the “limbo” under a string or a meter stick
- balancing on one leg
- bending over and tying your shoes
- trying to balance on a skateboard (definitely in grass… this could be very dangerous on a hard surface)
- doing a cartwheel
The possibilities really are endless, and I encourage my students to be as creative as possible. While they are developing these tasks, I walk around and, considering the fact that the students will probably fall down frequently during the physical tasks, I ask students if the task is reasonably safe in the space we have to conduct the experiment. If not, I suggest a safer alternative or simply tell them that their task is too dangerous and they need to come up with something else.
Additionally, I like to ask groups what kinds of data they will collect from the tasks. For example, repeatedly tossing a tennis ball in the air and trying to catch it may provide quantitative data (how many times they catch it vs. how many times they drop it, how long it takes them to toss it five times, how high they toss it) as well as qualitative data (did they catch it with both hands and pull it to their chest or with one hand high?, did they fall over when they tried to pick up a dropped ball?, were their feet moving around as they looked up or firmly in place?).
In determining what kinds of data students will collect from the tasks, students often “fine tune” the rules of their tasks to conduct a controlled experiment (e.g., you must throw the tennis ball over your head and not just in front of your body, you will be timed how long it takes you to toss the tennis ball and catch it five times, you have to try and catch it with one hand, etc.).
Control group vs. Experimental group
Finally, I make sure that students have at least a broad conception of the need for an experimental group and a control group. Some groups will do this by having some students be the control group by completing the tasks without spinning and then have the other members of the group be the experimental group and perform the same tasks after spinning. What I have found to be more common, however, is that all students perform the tasks without spinning (as the control group) and then perform tasks after spinning (as the experimental group). The advantage of this approach would be that it offers a larger data set (more students/test subjects) and, perhaps more importantly, allows more students to get in on the fun of the activity.
What I do not do, however, is micromanage their design. As I go from group to group, I notice little problems where they do not maintain strict control of the experiment (e.g., not having a set number or duration of spins for the spinning part, resulting in different degrees of vertigo depending on the student, as some may want to spin very slowly and others whip themselves around like a whirlwind).
Rather than pointing out all these little errors in their experimental design, I prefer to let them see these errors either while conducting the experiment, or in the follow-up lesson where they evaluate their lab reports looking for instances of experimental error. In short, their mistakes here provide powerful learning opportunities that they will hopefully transfer to more carefully designed experiments in the future.
If you teach on a block period, you may be able to have students conduct the experiment in the second half of the class. If you are on a traditional schedule, however, you will need to conduct the experiment on the next day as you will need around 60 minutes for students to perform all tasks and collect all the necessary data.
In either case, some groups will finish their design with time left over. I would suggest a few things in this case:
1. Ask students to use the internet to research physiologic vertigo to see if the information they find affects their hypothesis or inspires them to try different tests (e.g., knowledge that the eyes are involved in maintaining equilibrium might inspire students to test the effects of spinning blindfolded).
2. Have students complete the “control group” written tasks in class as they are safe to perform in a classroom. Keep in mind (without mentioning this students) that this introduces additional variables into their experiment (i.e., they are unlikely to be sitting in a chair at a desk when doing the written tasks in the field).
At the end of the class period, I tell students to prepare for the next day’s lesson: actually conducting their experiment. Since we will conduct the experiment outdoors, and since they will likely fall down frequently, I ask them to dress appropriately. This means different things in different climates, but almost always means not wearing your best outfit. In Southern California, this means bringing sunglasses, sunscreen, and dressing for the heat (perhaps by wearing shorts). No matter the locale, female students may need to be reminded not to wear skirts (this may be an issue if your school has uniforms) or heels. Students of both sexes should wear shoes rather than flip flops.
I also remind students that, even though we will be outdoors, they still need to bring all necessary supplies such as writing utensils and notebooks. I also recommend that they bring smartphones and/or digital cameras if they have them (for a full explanation of these materials, see the beginning of the next lesson).
Finally, I ask students to bring a completed copy of their experimental procedure so that they can follow their own design. It may be wise to collect procedures at the end of this period in case a student is absent on the day of the actual experiment.
If for some reason a group does not have their experimental design completed by the end of this period, I ask that they either show it to me after school or before school on the following day. I sometimes find it necessary to open my classroom after school to allow students to work and complete their design.
Please note: if you are teaching a block period and planning to both design and conduct the experiment in the same class period, you should make these announcements on the previous day so that students are prepared to go outside.