Research designs can be classified into three broad categories, according to the amount of control the researcher maintains over the research study. Although there are many resources for facilitating lessons and courses on student generated research, experimentation and investigation, the NSTA (National Science Teachers Association) STEM Student Research Handbook is by far one of the best supplements I have encountered. This handbook's chapter sampler will enable instructors to preview why this is such a powerful resource for both teachers and student alike!
In this lesson, students will examine one of the three types of research design - experimental research. In this kind of research study, the researcher controls the setting in which the research is conducted, manipulates the levels of the independent variable or variables, and then records the corresponding changes in the dependent variable or variables.
For guided practice we complete the Student Handout #2 - Research Design Table using the sample research project question: "How effective are plant-based insect repellents?" As we begin to explore the elements of the STEM Experimental Research Design we take a close look at the following components of any successful investigation:
1. Testable Question: How effective are plant-based insect repellents?
H0 - There is no significant difference between the effectiveness of plant-based versus traditional, chemical-based insect repellents.
H1 - Plant-based repellents are more effective than chemical-based insect repellents.
H2 - Plant-based repellents are less effective than chemical-based insect repellents.
3. Variables (Independent/Dependent):
IV - Various plant-based repellents, such as Corymbia citriodora or lemon eucalyptus extract, with different concentrations of the active ingredient PMD
DV - Potential dependent variables: total number of insect bites, size of insect bites, color and/or itchiness of insect bites, length of healing or recovery time, genus/species of insect that creates bites
4. Experimental Groups: Use of plant-based insect repellent of differing concentrations of the active ingredient with randomly selected subjects
5. Control Group: Use of the gold-standard, traditional, chemical-based repellent DEET (N, N-diethyl-3-methylbenzamide) at a commonly used concentration or corresponding concentrations of the active ingredient with randomly selected subjects
NOTE: The control group is the one group to which the experimental groups will be compared. In theory the control group receives the exact treatment as the experimental groups except it does not receive the change of the independent variable. As in this example, a control can also be a known standard, measurement, or level of the independent variable. In this case students proposed comparing our experimental group results to the results observed when using DEET, a known active ingredient in chemical-based insect repellents. It is important to note that for some experiments there is no designated control group and comparing the data collected from the experimental groups is sufficient.
CHECKPOINT: Ask students to justify or defend the NEED for a control group in our sample investigation.
6. Constants: Students suggested using the same subjects, using same volume or amount of insect-repellents, conducting the investigation in a similar geographical location with similar weather conditions, same application process for each of the repellents, same genus and species of insect
Students begin the research design process by practicing writing hypotheses and investigating the interdependence between creating a testable hypothesis and the design of an effective research project. MythBusters, Discovery Channel's cable television series, provides a fun backdrop for practicing the composition of hypotheses as well as the identification of other key components of the STEM Student Research Process.
Depending on the level of student and classroom culture I use either of the following Engage activities to get students excited about studying the research design process:
Create an Episode of MythBusters: Watch the MythBusters episode entitled “Exploding Pants”. Student lab groups will be asked to preview the MythBusters episode online, take notes on the episode using either the MythBusters Graphic Organizer or the MythBusters Research Design Guide and be prepared to view and discuss the episode with group members in class. Each group will then be asked to submit a proposal for â¨an upcoming episode of MythBusters in which they will either prove or dispel a myth of their choice or be provided suggestions from the instructor. Each group will be required to submit a proposal in writing outlining the myth, an experimental procedure, and materials needed to investigate the myth.
My Favorite Myth: Students will give a five minute group presentation detailing a myth of their choice or from a list provided by the instructor. Group members will share by explaining any additional research on the topic, form a hypothesis based on evidence discovered during research, background and/or an experiment performed, organize any collected data in a meaningful way, and formulate a conclusion based on the analysis of the evidence found.
In this section of the lesson our goal is to blend theory with practice with a portion devoted to direct instruction of content through lecture notes as well as guided exploration through the completion of the Student Handout #4 - Practicing Writing Hypotheses.
When mastering the ability to compose a "testable" hypothesis, students will:
- determine a specific variable to be tested
- determine how changes within the experiment will be measured or recorded
- predict an outcome of the experiment
The purpose of the hypothesis is to clearly define what will be tested as well as to define the limits of the experiment. The goal when composing a hypothesis is to connect the manipulated changes made by the independent variable with the effects on the measurements of the dependent variable. When introducing the concept of formulating a "testable" hypothesis encourage students to begin by composing a draft of their hypothesis using any of the following sentence starters:
1. If (IV) is related to (DV), then (predict the effect).
2. If the (IV) is (describe the changes), then the (DV) will (predict the effect).
3. (DV) will (predict the effect) when (IV), then (describe the changes).
In this section of the lesson, students practice identifying the independent and dependent variables and use this skill to begin designing their own research projects. The independent variable (IV) is the variable that is purposely changed by the investigator by varying the quantity or quality of this variable thus creating experimental groups. In theory, short experiments, such as those conducted by students as they begin to conduct independent research, should have one observable variable that can be measured either qualitatively or quantitatively. The dependent variable (DV) is the variable that changes in response to the independent variable and is oftentimes represented by the data that is recorded in our data tables.
Students begin with a checkpoint to assess their proficiency at this point in the lesson. Then small groups of 3 to 4 students are provided several descriptions of sample research projects and are instructed to work as a team to identify and chart the independent and dependent variables of each investigation. We have used several cooperative learning structures such as a gallery walk or museum to enable members of others groups to observe and learn from the efforts of other groups in our classroom community.
Students will complete the student research design table as they begin constructing independent research projects on topics of interest. Once individual or teams of students have brainstormed ideas for individual projects, background information must be collected in such a way that will enable students to apply the knowledge gained to the design of the proposed experiment.
The STEM Student Research Handbook suggests composing at least one background research question for each of the following categories (based on our sample investigation):
- Specific types or variations that can be studied (i.e. What is known about the use of [safety, efficacy of] insect repellents?)
- Handling/care/safety/ethics within a controlled environment (i.e. How do biotechnologists determine the most appropriate concentration of insect repellent?)
2. Independent Variable
- How it can safely and ethically be manipulated (i.e. How does the use of different active ingredients effect the safety of the insect repellent?)
3. Dependent Variable
- How changes can best be measured, recorded, and observed (i.e. What experimental methods will yield the most valid data when testing the effectiveness of insect repellent?)
4. Interdependence between the Entity and the Independent and Dependent Variables
- Previous research on the topic; what is already known about the possible relationships (i.e. How does the concentration of the active ingredient alter the effectiveness of the insect repellent?)
As we close this lesson students are given the opportunity to connect the research design process to their own lives as well as to our industry. This can be completed using any of the following written reflection strategies such as an Exit Ticket, Stop-and-Jot, or Quikwrite however reflections can also be conducted as small group discussions and Socratic Seminars.
It is extremely important for students to have an avenue for expressing their triumphs and tragedies as they move through the research design process. The following Research Design Process Reflection can help instructors identify a student researcher's "gots and needs" in order to provide just the right level of personalized support.
POTENTIAL REFLECTION QUESTIONS
1. How does science and technology (STEM) affect one’s daily activities?
2. How can we apply basic science principles and values in daily decision-making to our jobs in the biotechnology workplace?
3. In what everyday situations would someone have to rely on the scientific method?
4. Why is the scientific method necessary when conducting an effective, valid investigation?
5. Why do some experiments “turn out” while others do not?
6. Why is it important to communicate experimental results to others within AND outside our field?