Methods of Science Chapter 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 wet Inferences: 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