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Experimental Investigation. Involves a “fair test,” in which one variable (independent variable) is isolated and manipulated by the experimenter and the results are measured by a chosen criteria (dependent variable). All known variables have been identified
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Experimental Investigation Involves a “fair test,” in which one variable (independent variable) is isolated and manipulated by the experimenter and the results are measured by a chosen criteria (dependent variable). • All known variables have been identified • Has a research question, hypothesis, procedures, control, and conclusion • Conditions can be controlled.
Experimental Investigation Research Question: Do plants grow better with water or another liquid?
Independent Variable – A variable that you can directly change, or have control over. (What the scientist is changing) • What is tested by the scientist • What is changed by the scientist • Also known as manipulated variables
Dependent Variable – The factor, or outcome that will be measured in the experiment. •What is observed •What is measured •The effect caused by the independent variable. •The data •Also called responding variables
Control Group – the group in the experiment that is not given the treatment the other groups receive. •The group that is under “normal conditions” •Kept “normal” so scientist can see what would happen without the treatment.
Constants – things that are intentionally kept the same for each specimen in the experiment. •Things that could change but don’t •Kept constant (the same) by scientists •These allow for a fair test.
Do plants grow better in water or another liquid? • Research Question: Do plants grow better with water or another liquid • Hypothesis Ex: Plants will grow better in water because plants need water to live. • Gathering Data: Controlled experiment with one independent variable. • Independent Variable: Type of liquid given to plants • Dependent Variable: Measured growth of each plant • Constants: Conditions kept the same (such as amount of liquid, type of plant, soil, amount of sunlight)
Identify the Variables There are two kinds of variables we will be using to create a line graph: Independent / (Manipulated ) Variable – this is the variable that we change. Dependent / (Responding) Variable – this is the variable that responds to that change.
Identify Constants in an Experiment Constants are the things in an experiment that stay the same. There are many things in an experiment that are constant. Most things in your experiment should be constant.
Identify the Control in an Experiment • The control is a particular sample that is treated the same as all the rest of the samples except that it is not exposed to manipulated variables • Common examples: • Room Temperature • Water • No weight added or removed • No protection
Example 1 Sarah believed that oil poured faster when it was warmer. She created an experiment where she warmed the oil to different temperatures and timed how long the oil took to fill a beaker to 50 mL.
Independent/ Manipulated Variable – temperature of oil. Dependent/ Responding Variable – Time it took to fill a 50 mL beaker Constants – beaker , type of oil, amount of oil …… Control – room temperature oil.
Example 2 Sydney thought that the heavier a person was, the faster they would be able to roller blade down a hill. She created an experiment to see if she was correct. She got a skateboard and timed how long it took to reach the bottom of the hill. She then put different weights on the skateboard and timed how long it took to reach the bottom of the hill.
Independent/ Manipulated Variable – amount of weight Dependent/ Responding Variable – time to reach bottom of the hill Constants – type of skateboard, location of run ….. Control – Time without the weights
Example 3 Emilio believed that the more someone exercised the faster their heart would beat. He created an experiment that had 25 of his friends running in place. He timed their heart rate when they started running and then every 15 seconds for 30 minutes.
Independent/ Manipulated Variable – Portion of the exercise (beginning, middle, end) Dependent/ Responding Variable – Heartbeat Constants – Type of exercise, pace of exercise, the time of day they ran , the temperature ……. Control – Heart rate before exercise
Example 4 Jenny ‘s mom was telling her a story about how her grandmother would always add aspirin to the water before watering her plants. Jenny decided she would find out if it really made a difference and thought it probable did. Jenny hypothesized that the more aspirin she used, the more the plants would grow. She conducted an experiment with 4 different amounts of aspirin (including one without aspirin) and she used 10 bean plants for each amount. She used the same size pot, types of plants, water amounts, dirt, etc….
Independent/ Manipulated Variable – amount of aspirin. Dependent/ Responding Variable – plant height. Constant – type of plant, amount of light size of pot……. Control – The plant with no asprin.
