The Scientific Method • There is simply no fixed set of steps that scientists always follow, no one path that leads them unerringly to scientific knowledge.
“The Scientific Method” • Question or Problem 2) Hypothesize • Predict Consequences 4) Experiment • 5) Interpret Experimental Results
Experiments • An experiment is a test used to determine if there is evidence to support a hypothesis
What is a hypothesis? • A hypothesis is a guess or prediction about a phenomenon. • Hypotheses can be stated as positive or negative. • The “null” hypothesis predicts that there will be NO difference between experimental groups.
Write your own hypothesis • Write your prediction for the outcome of the radish seed experiment • You should also provide a REASON. • Why do you think the experiment will turn out the way it will?
What is a theory? • A theory is an explanation that has a very large amount of evidence to support it. • A fact is an observation about nature. A theory is an explanation. So a theory can never “become” a fact.
Experiment Titles • Usually, experiments are titled in a format like this: • “The Effect of _______ on _________” • Sample title: “The Effect of Light on Growth of Radish seeds”
Experimental variables • The ONE factor that you cause to be different between experimental groups is the MANIPULATED variable (also called INDEPENDENT variable). • Sample: In the radish seed experiment, the manipulated variable is”Amount of Light”
Experimental variables • The factor that you measure as the outcome of the experiment is called the RESPONDING variable (also called DEPENDENT variable) • In the radish seed experiment, the responding variable is ___________. • The responding variable is LENGTH of STEM, measured in millimeters.
Constants • All other factors in the experiment must be controlled so they are the same for all groups. • Examples of constants in radish seed experiment: • Type of Petri dish type of seed • Number of seed paper towel • Water, Location temperature
Measurements • Obtain a flexible plastic ruler and measure the length of the radish seeds today in millimeters. • Record your data and your partner’s data in the data table.
Observing plant growth: • Take bean and pea seeds and put them in containers of soil under our light source. • Water them consistently. • Each day in class, take note of any changes that you observe.
Measure the responding variable • Draw a data table for recording radish plant sizes Growth (mm) in Light Growth (mm) in Dark Date
Writing an experiment description • Title • Hypothesis • Short description of procedure • Identify control and experimental groups. • Name the manipulated, responding variables • Identify five constants