xp-evaluation - EXPERIMENTAL DESIGN REFERENCE Scenario A...

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EXPERIMENTAL DESIGN REFERENCE Scenario: A group of students is assigned a Populations Project in their Ninth Grade Earth Science class. They decide to determine the effect of sunlight on radish plants. They grow 12 radish plants in 4" clay pots with 25 mL of water daily and 100 g of potting soil in 24 hours darkness, 12 hours sunlight/12 hours darkness, and 24 hours sunlight. (They use Grow-Lights to simulate sunlight.) After 5 days, they measure the height of all the plants in each pot. 1. TITLE: Communicates what your experiment is about. The Effect of (the independent variable) on (the dependent variable.) Example: The Effect of Sunlight on the Height of Plants. 2. HYPOTHESIS: Communicates what you think is going to happen in the experiment. If (the independent variable) is (increased, decreased, changed) , then ( the dependent variable) will (increase, decrease, change.) Example: If the sunlight is increased, then the height of the plants will increase. 3. INDEPENDENT VARIABLE: (I.V.) Also called the Manipulated Variable . The variable you purposely change or manipulate. Will be the CAUSE of the changes you measure. Example: The Sunlight LEVELS: The values you choose for your Independent Variable. Example: 24 hours of darkness, 12 hours of sunlight/12 hours of darkness, and 24 hours of sunlight. TRIALS: The number of times each level is repeated. Could be the number of seeds in a pot, or the number of fish in a fish bowl. Example: 12 radish seeds in each pot = 12 trials for each level of sunlight 4. DEPENDENT VARIABLE: The variable that responds. Also called the Responding Variable . The variable you will measure after the experiment is set up. Will be the EFFECT of the action you took. Example: The Height of the Plants. 5. CONSTANTS: All the other variables that remain the same for all the trials. Must be quantified. (Include numbers.) Example: 4" pots, 100 g potting soil, 25 mL water daily 6. CONTROL: A level that does NOT contain the independent variable. The NO TREATMENT GROUP or NORMAL TREATMENT GROUP. Gives you a way to detect hidden variables. Example: the level in the above scenario that most acts like NORMAL for plants would be the 12 hours sun/12 hours dark. You are comparing the 24 hours darkness and 24 hours sunlight to the normal situation for plants.
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EXPERIMENTAL DESIGN FORMAT: This format is required for every experiment! NOTE: THIS IS NOT THE DATA TABLE!! Title: The Effect of Sunlight on the Height of Plants. Hypothesis: If the sunlight is increased, then the height of the plants will increase. I.V. Amount of sunlight (hours) Levels: 0 12 24 Trials: 12 12 12 D.V. The Height of plants (cm) Constants: (1) 4" pots (2) 25 ml water daily (3) 100 g soil Controls: 12 hours sunlight/12 hours darkness CHECKLIST FOR EVALUATING YOUR EXPERIMENTAL DESIGN: 1. TITLE: Does the title clearly identify both the independent and dependent variable? Have you used the words THE EFFECT OF and ON?
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