Or what changes during experiments…. What are variables? Or what changes during experiments….

Hypothesis Is written in the form of a statement. Can use If/then statement format. Is an “educated guess” based on past knowledge/experience and research. Must be testable (ex: plant height, # of flowers grown). Example: If Speedy fertilizer is added to the petunias, then they will grow more flowers than petunias that do not receive Speedy fertilizer.

Let’s use this experiment to figure out the variables. I would like to figure out which plant fertilizer will make my petunias grow the most flowers over a 3 month period. I am going to try 3 different fertilizers. Speedy Fertilizer Nature’s Best Fertilizer Home Grown Fertilizer

Control Variable is used as a constant and unchanging standard of comparison in scientific experimentation. It is used to compare all other experimental groups. In our experiment about fertilizer, the petunia plant we would use as the control is the one we DO NOT fertilize.

Independent Variable What is tested by the scientist What is changed by the scientist Also known as the “manipulated” variable. In our experiment, the independent variable is the type of fertilizer we are going to test since we are changing the types of brands.

Dependent Variable What is observed. What is measured. The “effect” caused by the independent variable. The data you collect. Also called responding variables In our fertilizer experiment it would be the number of flowers on the plants as they grew over 3 months.

Constants All the factors that have to remain the same throughout the experiment so you are only testing 1 independent variable. In our fertilizer experiment, our constants would be: Same type of petunia plant. Same soil. Same pot size. Same amount of sunlight, water, temperature. Any others?????

So in conclusion, our variables are: Controlled variable (the standard): Petunia with NO fertilizer. Independent variable (you change this): Types of fertilizer. Dependent variable (may or may not change: amount of flowers on Petunia plant. Constants: Same type of plants, same pot size, same soil, same amount of water, sunlight and temperature.