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A Controlled Experiment Part of the scientific method.

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Presentation on theme: "A Controlled Experiment Part of the scientific method."— Presentation transcript:

1 A Controlled Experiment Part of the scientific method

2 Variables A factor that can change. A variable can change other factors when it changes. A factor that can change. A variable can change other factors when it changes. Examples of variables: -Temperature-Light - Open vs. Closed container -Location-Time-Elevation-Pressure

3 Quantitative and Qualitative A Quantitative Variable is one that is measured using numbers. Examples: temperature is measured in degrees, length can be measured in centimeters. A Quantitative Variable is one that is measured using numbers. Examples: temperature is measured in degrees, length can be measured in centimeters. A Qualitative variable is one that can not be measured in numbers, but by its qualities. Such as bright, clear, rough, smooth, pain. A Qualitative variable is one that can not be measured in numbers, but by its qualities. Such as bright, clear, rough, smooth, pain.

4 Independent vs. Dependent Variables The dependent variable is a factor that changes because the independent variable changes. However the independent variable is not changed by the dependent variable. The dependent variable is a factor that changes because the independent variable changes. However the independent variable is not changed by the dependent variable. Example: Elevation and Boiling temperature of water. The boiling temperature of water changes because of changes in elevation. Changes in the boiling temperature of water do not change elevation. Example: Elevation and Boiling temperature of water. The boiling temperature of water changes because of changes in elevation. Changes in the boiling temperature of water do not change elevation.

5 Graphing Variables The Independent variable is always graphed on the X axis. The Independent variable is always graphed on the X axis. The dependent variable is always graphed on the Y axis. The dependent variable is always graphed on the Y axis.

6 Hypothesis vs. Theory Hypothesis is a testable statement that can be proven false. Hypothesis is a testable statement that can be proven false. Can be a prediction of an outcome Can be a prediction of an outcome Hypothesis can become a theory once it is supported by enough evidence. Hypothesis can become a theory once it is supported by enough evidence. Theories are supported by multiple observations or experiments A theory may be proven false or modified when more data is collected Usually the lest complicated explanations

7 Control -A variable or factor that does not change in the experiment. It remains constant. In a Controlled experiment only one variable is allowed to change at a time. Everything else remains constant.

8 OBSERVATIONS: Flies land on meat that is left uncovered. Maggots appear on the meat. HYPOTHESIS: Flies produce maggots. VARIABLES Controlled Variables: jars, type of meat, location, temperature, time Independent Variables: gauze (keeps flies away from meat) Uncovered jars Covered jars After several days Maggots appear No maggots appear Dependent Variable: whether maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur. Francisco Redi & Spontaneous Generation

9 Replicates In an experiment multiple copies of the experiment are done at the same time. In an experiment multiple copies of the experiment are done at the same time. This is to ensure that the results are accurate (true) and not due to a mistake, error or chance event. This is to ensure that the results are accurate (true) and not due to a mistake, error or chance event.

10 Treatments Set of variables in the experiment that are the same in each group of replicates. Set of variables in the experiment that are the same in each group of replicates. 2 Treatments 2 Treatments CoveredUncovered


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