Experimental Design & Scientific Methods SC. 8. N. 1 Experimental Design & Scientific Methods SC.8.N.1.1 Define a problem from the eighth grade curriculum using appropriate reference materials to support scientific understanding, plan and carry out scientific investigations of various types, such as systematic observations or experiments, identify variables, collect and organize data, interpret data in charts, tables, and graphics, analyze information, make predictions, and defend conclusions. ESSENTIAL QUESTION: How do hypotheses, variables, data collection/ analysis, and experimental design ensure that results are reliable and the experiment is fair?

Bellringer Jules wanted to know whether the eating behavior of goldfish is affected by music. He set up a fish tank. Every day, Jules played music for the fish and measured how much the fish ate. What is Jules missing from this experiment? A control group A measurable result Different types of fish An outcome variable (dependent variable)

I DO GUIDED NOTES

Introduction to the Scientific Method: Anyone who has ever read a mystery novel or seen a “whodunit” on TV has seen the scientific method in action. Anyone who has ever tried to figure out what happens to the refrigerator light when you close the door, or where that other sock goes after you put it in the dryer has used the scientific method. The scientific method is not a mystical, incomprehensible process that can only be done by scientists. Instead, it is a logical, organized mechanism for identifying and researching a problem, and devising a strategy for solving it.

1. Determining the problem or question. In this step, you (the researcher) must decide what it is that you will be studying. This sounds like a simple procedure, but it is actually very important. It identifies exactly what you wish to learn and it allows you to focus only on that material. Making observations helps you identify a problem that can be tested.

Experimental Design A. General Question: What color of flower attracts the most insects? B. Initial observation/background information In the field adjacent to campus, there seem to be more insects on the purple flower plants vs the white flower plants.

2. Development of a hypothesis. The hypothesis is NOT an (educated) guess! Instead, a hypothesis is a prediction based on observations and/or research. Once you have identified a problem/question, conduct some research based on your observations. Use that information to help devise a hypothesis. An important aspect of the hypothesis is that it should answer the original question, and it should be testable!

Experimental Design A. General Question ? B. Initial observation/background information C. Refine to a Hypothesis If a plant has purple flowers, then it will have more insect visits to its purple flowers compared to the insect visits to white flowers on an adjacent plant because bees can see its color easier.

3. Identify Variables There can only be ONE variable tested on an experiment. This is called the tested (independent) variable and is the factor that you change between groups when you set up the experiment. The outcome (dependent) variable is the result of your independent variable. It is how you are measuring (data) what happened as a result of the tested variable. (EX. Because I used fertilizer (Independent Var.) in some plants, the plants grew taller (Dependent Var.) Controlled variables are all the factors that you keep the same for EVERY group in your experiment.

Experimental Design Flower Color / Number of Insect visits A. General Question ? B. Initial observation/background information C. Refine to a Hypothesis …If…then…. D. Design Test of Hypothesis Independent/Dependent variable Flower Color / Number of Insect visits

4. Design an experiment to test the hypothesis. Design an experiment to test your hypothesis that includes only one independent variable. Your hypothesis will not be “wrong” or “right”. The data supports your hypothesis or it doesn’t. As you conduct your experiment, you will collect your data, analyze your results and form logical conclusions.

Experimental Design E. Gather Data A. General Question ? B. Initial observation/background information C. Refine to a Hypothesis …If…then…. D. Design Test of Hypothesis Independent/Dependent variable E. Gather Data 10 minute Observation Interval White Purple 1 5 12 2 8 9 3 15 4 21

5. Conduct the experiment and collect the data. Run the experiment that you have so carefully constructed. In this step, you will be measuring the dependent variable. The dependent variable is the factor that is being observed or measured. Any pieces of information that you collect regarding the dependent variable are called DATA.

Experimental Design F. Analysis A. General Question ? B. Initial observation/background information C. Refine to a Hypothesis …If…then…. D. Design Test of Hypothesis Independent/Dependent variable E. Gather Data F. Analysis

6. Draw Conclusions From Your Data Here, it is stated directly whether the hypothesis was supported or not. If your hypothesis is supported, you may need to conduct more trials in order to gather additional data so that your conclusion can be stronger. If it is not supported, design a test for a new Tested (independent) Variable.

Experimental Design G. Conclude A. General Question ? B. Initial observation/background information C. Refine to a Hypothesis …If…then…. D. Design Test of Hypothesis Independent/Dependent variable E. Gather Data F. Analysis G. Conclude In this field, the purple colored flowers receive a higher number of insect visits than the white flowers.

WE DO COLLABORATIVE ACTIVITY TEACHER NOTE: Several resources are provided. Complete the activities that you feel your students need the most.

Answer in your Log book page 8 Question #1 Jules wanted to know whether the eating behavior of goldfish is affected by music. He set up a fish tank. Every day, Jules played music for the fish and measured how much the fish ate. What is Jules missing from this experiment? A control group* A measurable result Different types of fish An outcome variable (dependent variable)

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Question #2 Denise and David are testing how plants respond to fertilizer. They use three plants for the experiment. The first is given a cup of Fast Grow fertilizer with no water. The second is given a teaspoon of SunLight fertilizer with a cup of water. The third plant is given no fertilizer with a cup of water. Denise and David will not be able to draw a valid conclusion from their result. Which of the following statements explains why? There are not enough different types of plants. There is no test variable (independent variable). Results of the experiment need to be presented in a graph. More than one test variable (independent variable) has been changed in the experiment. CORRECT ANSWER: D

Question #3 Allison and Heather are going to conduct an experiment to see whether salt affects the growth of plants. They assemble five groups of identical plants and give the plants in each group water with a different salt concentration. What is the outcome variable (dependent variable) for their experiment? Salt concentration in plant tissue Salt concentration in plant water Amount of water absorbed by plants Average mass of plants in each group CORRECT ANSWER: D

We DO Question #4 The graph below shows which wavelengths, in nanometers (nm), and corresponding colors of light are absorbed by the plant molecule chlorophyll a. Chlorophyll a is one of the molecules that plants use for photosynthesis. Which of the following would be an accurate analysis of the information shown? The least effective color of light for photosynthesis appears to be green. The lease effective colors of light for photosynthesis appear to be orange and red. The most effective wavelengths of light for photosynthesis are between 450 and 550 nm. The lease effective wavelengths of light for photosynthesis are between 600 and 700 nm. CORRECT ANSWER: A