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## Experimentation

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**Variables**• Variable = an aspect of events or things that differs according to the particular event or thing being considered but has a particular value for a given event or thing at a given time • Ex. Variable = weight Things = persons Different persons weigh different amounts but a single person weighs a certain amount at a given time.**Variables are Pervasive**• Every dimension by which an entity or event can be described can be considered a variable.**Experiments and Variables**• Experiments are conducted to attempt to find out the relationships among variables.**Quantifying Variables**• Variables can be quantified by measuring their different values.**Functional Relationships**• Variables are functionally related when the value of one variable determines another. • This can be stated mathematically: Y = f (X). The value of the variable Y is a function of the value of the variable X. • Ex. Running Speed = f (weight carried)**Experimental Design**• Experiments must be carefully designed to determine the functional relationships among variables. • The influence of variables other than those being tested must be controlled.**Experimental Variables**• Independent Variables • Dependent Variables • Control Variables**Independent Variables**• Directly manipulated by the experimenter and determined before the experiment begins • Experiments are designed to see how manipulating the independent variable will effect the dependent variable.**Example of an Independent Variable**• A runner is clocked sprinting for 100 yards with a backpack 6 times carrying 0, 10, 20, 30, 40 and 50 pounds. • The weight in the backpack is the independent variable**Dependent Variables**• The values of the dependent variable are the product of the experimental conditions. • They are a function of the values of the independent variable. • Dependent = f (Independent) • They are measured under each of the values of the independent variable.**Example of a Dependent Variable**• A runner is clocked sprinting for 100 yards with a backpack 6 times carrying 0, 10, 20, 30, 40 and 50 pounds. • The runner’s speed is the dependent variable**Control Variables**• Control variables are set so that they cannot systematically affect the relationship between the independent and dependent variables. • The average value of a control variable should not change as the independent variable changes.**Example of Control Variables**• A runner is clocked sprinting for 100 yards with a backpack 6 times carrying 0, 10, 20, 30, 40 and 50 pounds. • The time that the 6 races are run is a control variable and should be set so that the runner doesn’t get more and more tired with each race.**Ways of Setting Control Variables**• Have no variation of the control variable among different experimental conditions. • Have the same distribution of the control variable among the different experimental conditions. • Have the values of the control variable randomly assigned among the different experimental conditions.**Variables and Hypotheses**• Experimental scientists must try to relate some terms of a hypothesis to dependent variables and some of them to independent variables.**Hypothesis Testing**• A well designed experiment will permit observations under controlled conditions and reveal the relationship between independent and dependent variables and thus of the hypothetical terms.