Methods of ScienceChapter 1.3 pages 16-21

At the end of this chapter you should be able to….

• Describe the difference between an observation and an inference.

• Differentiate among control, independent variable and dependent variable.

• Identify the scientific methods a biologist uses for research.

Scientific Method

• The scientific method generally follows the following pattern:

– Ask a question– Make observations– Form a Hypothesis– Experiment– Collect and analyze data– Draw conclusions

Ask A Question• Scientific inquiry begins with observation,

observation is the act of noting or perceiving objects or events using the senses

• Combining your observation with your past knowledge allows you to make inferences, or logical conclusions.

Observation vs. Inferences

• Inferences are an explanation for a observation that you have made.

• Inferences often change when new observations are made.

Observation: The grass is wetInferences: it rained

the sprinklers went off

Hypothesis

• a hypothesis is a TESTABLE explanation for your question.

– this statement can be tested by additional observations or experimentation

– an educated guess based on what is already know

Experiment

• experiment – a planned procedure to test a hypothesis

• controlled experiment – an experiment where an experimental group is compared to a control group– control group is a group in an experiment that

receives no experimental treatment– An experimental group is the group exposed to

the factor being tested

Experimental Design

• both control and experimental groups are designed to be identical except for one variable

• the factor that is varied in an experiment is called the independent variable

• the variable that is measured in an experiment is called the dependent variable

• a constant is a factor that remains fixed during an experiment

Collect and Analyze Data

• Data is any information gained from observations.

• 2 types: • Quantitative – measureable or countable

» 3 meters long» 4 marbles» 50 kilograms» 35 degrees Celsius

• Qualitative – describable, not measureable » red flowers» smells like fresh baked cookies» Tastes bitter

Collect and Analyze Data

• A graph of the data makes the pattern easier to grasp.

• On a graph, the x axis represents the independent variable

• the y axis represents the dependent variable

Conclusion

• once data are collected and analyzed, a hypothesis is either supported or rejected

• even when a hypothesis has not been supported, it is valuable.

• a hypothesis can be supported, but never proven because another experiment with new data can alter the conclusion

• Publication– scientists often publish the results of their

experiments for review and use by other scientists