Answer :
At least one. In order to establish a causal link between the variable you are modifying and the observed response.
A controlled scientific investigation of particular factors is known as an experiment. A variable is a substance that has multiple possible values. For instance, one variable might be how quickly an object descends a ramp, while another might be how steep the ramp is. Any experiment must have a manipulated variable and a responding variable, at a minimum.
A variable that has been altered by the researcher is known as a manipulated variable. An independent variable is another name for a controlled variable.
The researcher predicts that a variable will change if the controlled variable changes; this variable is known as a responsive variable. A dependent variable is another name for a responsive variable.
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