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Remember... Independent Variables answer the question... What do I change? Dependent Variables answer the question... What do I observe? Controlled Variables answer the question... What do I keep the same? A scientist is testing the effect of light and dark on the behavior of moths by turning a light on and off. What is the Independent variable? The independent variable is the amount of light and the moth's reaction is the dependent variable. A change in the independent variable directly causes a change in the dependent variable. The time it takes to run a kilometer depends on the amount of exercise a person gets. What is the IV (Independent Variable)? IV = Amount fo exercise DV= Time to run a kilometer The higher the temperature of water, the faster the egg will cook. What is the DV(Dependent Variable)? DV= Time needed for the egg to cook IV= Temperature of the water An investigation was done to see if keeping the ligghts on for different amounts of time each day affected the number of chicken eggs layed. What are the two variables? Variable #1= Hours (amount) of light Variable #2= Number of eggs Manipulated Variables If a variable is deliberately changed in a situation, it is called a Manipulated Variable MV=IV What variable is being manipulated in the following situations? The amount of pollution produced by cars was measured for cars using gasoline containing different amounts of lead? Answer: Amount of lead in gasoline Lemon tress receiving the most water produced the largest lemons... Answer: The amount of water. Responding Variable: The variable that may change as a result of the maniplulation is called the responding variable. RV=DV Identify the manipulated (IV) variable and the responding (DV) variable in the following situations.... More bushel of potatoes will be produced if the soil is fertilized more... Answer: MV: Amount Fertilizer RV: # of bushels of potatoes 5 groups of rats are fed identical diets except for the amount of vitamin A that they receive. Each group gets a different amount. After 3 weeks on the diet, the rats are weighed to see if their weight has changed. What is the MV and RV? MV= Amount of Vitamin A(IV) RV= Weight of rats (DV) Now! Let's put the data from the variables into a table and learn how to graph the data. Usually the manipulated variable (IV) is written on the left, but not laways. Lenght of Drop (Cm) Height of Bounce (cm) 10 8 50 40 70 56 The Independent Variable is ALWAYS graphed on the X-axis The Dependent Variables is ALWAYS graphed on the Y- axis D Dependent R Responding Y axis M Manipulated I Independent X- Axis