Introduction to the Scientific Method

1. Introduction to the Scientific Method Developing and Applying Basic Concepts

2. Scientific Method

3. Approach to Understanding Experimental Design • An effective method for teaching students to design experiments begin with concrete investigations of phenomena that enable students to quickly manipulate materials and see results. • Every experimental approach displayed in class has the potential to be manipulated to obtain desirable results and needs to be explained using the key components of the scientific method throughout the entire course of the year for every experiment.

4. Components of an Experiment • Before students can build the confidence required to manipulate an experiment, they need to be educated on the key components of experimental design. • What is a variable? It is the thing or factor that can be assigned or take on different values in an experiment. • What is the independent variable (manipulated variable)? It is the variable that is changed on purpose by the experimenter. • What is the dependent variable (responding variable)? It is the factor or variable that may change as a result of changes purposely made in the independent variable. • What are constants? Constants are the factors in an experiment that are kept the same and not allowed to change or vary. • What is the control? It is the part of the experiment that serves as a standard of comparison.

5. What is an Experiment? • Simply stated, an experiment is a test of a hypothesis. It determines if purposely changing the independent variable does indeed change the dependent variable as predicted. • One of the biggest mistakes in the science classroom is confusing an experiment for a demonstration. • An experiment tests for a potential cause and effect relationship between variables, where a demonstration presents a previously known phenomena.

6. Defining a Hypothesis • What is a hypothesis? A hypothesis most commonly known as an if…..then….. statement, is a prediction of the relationship of an independent and dependent variable to be tested in an experiment; it predicts the effect that the changes purposely made in the independent variable will have on the dependent variable. • The hypothesis should state in a clear and concise way how the student, through the construction of an educated guess, predicts that the dependent variable will respond to the manipulated variable. • Since the hypothesis is tested by an experiment, the effect of the independent and the dependent variable need to be measurable. • Examples: • "If a plant receives fertilizer [having fertilizer is the independent variable], then it will grow to be bigger than a plant that does not receive fertilizer [plant size is the dependent variable]." • "If I put fenders on a bicycle [having fenders is the independent variable], then they will keep the rider dry when riding through puddles [the dependent variable is how much water splashes on the rider]."

7. Identifying Components of an Experiment • It is essential to have students practice identifying key components of a generated experimental design. • It is also important to have students generate experimental design diagrams to gain practice identifying components of an experiment as well as helping them to focus on the key ideas of constructing experiments with one independent variable. • It is important for experiments to contain one independent variable, so that the observed effect will indeed be due to that variable.

8. Constructing an Experimental Design Diagram • Steps for writing an experimental design diagram for an experiment with one independent variable. • Write a title: The Effect of the Independent Variable on the Dependent Variable. • State a Hypothesis: If the (independent variable) is (describe how you changed it), then the (dependent variable) will (describe the effect). • Write your independent variable (IV:). • Divide the bottom two rows into columns; one column for each level of the independent variable. Write the levels of the IV in the columns. If one of those levels is the control for the experiment, put the word control under that level. • In each column write the number of repeated trials conducted for each level of the independent variable. • Put your dependent variable (DV:) below the rectangle. • Write a list of the constants (C:).

9. Practice Evaluating Experimental Designs • Students can spend time evaluating generated experimental designs to gain an increased skill for identifying key components of an experimented. • Below is a checklist that students can use during this process: • Does the title identify both the independent and dependent variables? • Does the hypothesis clearly state how you think changing the independent variable will affect the dependent variable? • Is there an independent variable? • Are the levels of the independent variable clearly stated? Are there enough levels of the independent variable tested? • Is there a control? • Are there repeated trials? Are there enough of them? • Is the dependent variable clearly identified and stated? • Is the dependent variable operationally defined (measurable)? • Are the constants clearly identified and described? • Did the experimental design diagram include all of the parts? • Was the experiment creative? Was it at an appropriate level of complexity?

10. Summary of Key Components of an Experiment • Title • Hypothesis • Independent Variable • Levels of Independent Variable • Control • Repeated Trials • Dependent Variable • Measures of Dependent Variable • Constants • Quantitative data is information gathered from counts or measurements using scales having equal sized intervals and a zero value. • Qualitative data is verbal descriptions or information using scales without equal intervals or zero points.