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The Scientific Method


 The Scientific Method


In your online Biology 20 course, we don't have the opportunity for you to move through the entire scientific method in a single investigation. The scientific method is an important understanding for Biology 20 and for life! When you understand the scientific method, you are able to critically assess scientific claims because you understand where valid scientific information comes from.

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You will be asked to do parts of a lab report in Biology 20. In the future, you will likely be asked to do a full lab write up. Although the preferences of certain teachers will vary, lab reports will likely include a question, an hypothesis, a procedure or experiment, observations or data, analysis or results, and a conclusion. Often reports will also include a research section or bibliography showing the research that you engaged in prior to performing the experiment.


Each scientific investigation starts with a question.


As shown above, sometimes that question arises from observation and research. Some investigations have more than one question, but it is best that each question is testing only one manipulated variable. For example, "How does the amount of water provided to a plant impact its height?" 

A hypothesis provides a possible explanation or answer to your question.


It is often phrased in an "if... then" manner. So your hypothesis may read "If plants are given more water, then they will grow taller". Your hypothesis is an educated prediction. It is okay if you are wrong! Science progresses when researchers get results that are counter to what they expected. Never change your hypothesis to match your results!

How to Write a Hypothesis

A good hypothesis helps a researcher limit an investigation to the effect of one manipulated variable at a time. This allows a clear interpretation of observations. To develop a good hypothesis, you need to establish the variables that you are studying and make a prediction on how those variables interact. At this stage in your scientific career, it is best to create a simple hypothesis. The process to form a hypothesis has two parts.

  1. Define your variables. Determine which variable will change as you manipulate another. Consider the following question: "Is the rate of cellular respiration affected by the temperature of germinating seeds?" 

    The temperature of the germinating seeds is the manipulated (independent) variable. The rate of respiration is the responding (dependent) variable.

  2. State the relationship between the two variables in an "if . . . , then . . ." statement. If the manipulated variable affects the responding variable in such a way, then the responding variable should change in such a way when the manipulated variable is changed. For example, using the above temperature related question:

    If the rate of respiration of germinating seeds is dependent on temperature, then seeds under warmer conditions will consume oxygen at a faster rate than seeds at lower temperatures.

Nothing should be left to guesswork!


Once you have a question, you need an experimental design to test your question. A procedure is like a recipe for your experiment; anyone else should be able to follow it exactly and get the same results. Procedures are often written in numbered points for simplicity. Your procedure should include specific amounts, techniques, times, instruments, equipment, chemicals, etc.
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Collect and interpret.

Data collection occurs throughout the experiment and includes data on the manipulated, responding, and controlled variables. Ideally, you will have controlled the controlled variables and the manipulated variable so that the only measurements that needs to be made during the experiment are for the responding variable. If your data is numeric, decide ahead of time to what degree of accuracy you will record your data. This collection of data is sometimes called your results.
Your results alone do not provide an answer to your question. They must be considered carefully. Your data analysis is where you discuss whether your results are reliable and valid. Perhaps the temperature of the room changed when it was supposed to be controlled. You would want to discuss the possible impact to your experiment. Often, your teacher will provide some questions for consideration in this section. Eventually, you will be expected to discuss the validity and reliability of your results without guidance from your teacher.

Review your hypothesis.

This is when you finally get to state your conclusion. Your conclusion should either prove your hypothesis, disprove your hypothesis, or state that your results can neither prove or disprove your hypothesis. The point of science is not to get it right the first time. It is about learning and trying again. That is why the Scientific method is often shown as circular. If your experiment did not prove or disprove anything, that is okay! You are just learning how to be a scientist.