Biology
The Scientific Method
The Scientific Method
The Scientific Process
· Observing and stating the problem
· Questions about observations (forming a hypothesis)
· Testing the hypothesis (Experimentation)
· Record and analyzing data
· Forming Conclusions
· Replicating the work
Observing and stating the problem
Science is ultimately based on observation (perceiving objects or events using one of the five senses)
Observations often lead to questions ---> which lead to experiments to answer the questions.
Questions about observations (forming a hypothesis)
Hypothesis – is a possible explanation, a preliminary conclusion, or even a guess about some event in nature. Hypotheses can never be proven, only supported or rejected.
1. If repeated experiments consistently disprove the prediction, then we can assume that the hypothesis is false.
2. If repeated experiments consistently support the prediction, then we can only assume that the hypothesis is supported.
A hypothesis also needs to be a testable statement. What is wrong with the hypothesis below under the “bad” heading?
Good1. Plants will grow taller when given Miracle Grow.
2. Girls will score higher on math tests than boys.
3. Hermit crabs choose colorful shells over drab shells. / Bad
1. Plants will grow better when given Miracle Grow.
2. Girls are smarter than boys.
3. Hermit crabs like colorful shells.
A hypothesis is then tested by experimentation
Experimentation – Designing a controlled experiment
Experimentation - a planned procedure designed to test the hypothesis. All experiments must have at least two test groups:
1. Experimental Group – the group in which on factor or treatment is varied
2. Control Group – receives no treatment, used to compare
3. Variable – a condition of an experiment that is subject to change and that may influence an experiments outcome
Why do we need to have a control group?
1. Controls are a necessary basis for comparison with the experimental group
2. Allows conclusions to be made about the effects of experimental manipulation
Example of an experimental design
Hypothesis: Plants will grow taller when given Miracle Grow.Plants A & B are both given the same amount of light, water, and are stored at the same temperature. Plant A is given Miracle Grow.
All the variables are kept constant except the one you are testing. /
Independent Variable - the factor you change, what you do to your exp. group. (Miracle Grow)
Dependent Variable - what happens as a result of that treatment, what you are measuring (height of plant)
How can you keep these straight? The “I”ndependent variable is the one that “I” change.
Record and analyzing data
A scientist carefully collects and organizes data from the experiment. Data should always be presented in a neat fashion, usually tables or graphs.
Data Table ExampleIs there anything missing from this table? / A neat Graph
Conclusions
Based on your data, you can now determine whether the hypothesis was supported or refuted. Remember, you can never prove your hypothesis, only support or reject it.
1. If your data rejects your hypothesis, you must come up with a new hypothesis to test
2. If your data supports your hypothesis, your experiment should be carried out again to support it more. If your hypothesis is supported enough, you can form a theory.
- A Theory is an explanation for natural events that is based on a large number of observations.