Steps to the Scientific Method

Question/Purpose

HypothesisExperimentAnalyze Data

Conclusion

Research

Variables●Independent Variable – the variable that is manipulated by the experimenter. (I change the independent variable.)

●Dependent Variable – the effect (or outcome) that is measured at the end of the experiment (depends on the independent variable)

Constants●A constant is something that stays the same throughout the experiment.

Control●The control is the standard of comparison in an experiment. (Not all experiments have a control.)

Example ExperimentMrs. Davis wishes to see what type of fertilizer will help her plants grow faster. She buys three types of fertilizer and 4 of the same type of plant. She puts a different type of fertilizer in each of the pots of three plants and leaves one plant without any fertilizer. She is careful to give each of the four plants the same amount of water and sunlight.

Independent Variable

●The independent variable is the type of fertilizer because it is controlled by the experimenter, Mrs. Davis.

Dependent Variable

●The dependent variable is the growth of the plant because it will change based on the type of fertilizer it is given. It is also the outcome that is measured at the end of the experiment.

Control●The control in this experiment is the plant that received NO fertilizer. Since this plant received no “help” with its growth, Mrs. Davis can use it as a standard to which the other three can be compared. This will tell her how effective the fertilizers really were!

Constants

●The constants in Mrs. Davis’ experiment were the type of plant, the amount of water and the amount of sunlight. These all were the same about each plant or were given to each plant in equal amounts.

Now You Try!Ms. Brown wants to see if music will help her plants grow faster. She buys four plants of the same type and size and gives each the same amount of sunlight and water. She plays classical music for one, rap music for another, and country music for a third. The fourth plant is kept in a quiet spot with no music. She measures the height at the end of each month and graphs her results.

Now You Try It!1. What is the independent

variable?

2. What is the dependent variable?

3. What are the constants?

4. What is the control?

Now You Try!Mr. Mason loves popcorn! He decided to design an experiment to testwhether frozen popcorn would popbetter than unfrozen popcorn. He tested two bags of popcorn. Thepopcorn bags were the same brand,equally fresh, stored for the sameperiod of time, and popped in the samecorn-popping machine. One bag wasstored in the freezer and the other bagwas stored at room temperature.

Now You Try!1. What is the independent

variable?

2. What is the dependent variable?

3. What are the constants?

*There isn’t a control in this experiment.*

Now You Try!Mr. Holt caught two boys throwing paper airplanes on the science hall. They were experimenting to see if the type of paper used would affected the flight time of the plane. Can you help these boys design a good experiment using the scientific method?

Now You Try!

1. What is the independent variable?

2. What is the dependent variable?

3. What are the constants?