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Scientific Method. Biology. What is science?. Science is an organized way of using evidence to learn about the natural world. What is the goal of science?.

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Scientific Method

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Scientific Method


What is science?

Scienceis an organized way of using evidence to learn about the natural world.

What is the goal of science?

  • The goal of science is to investigate and understand the natural world, to explain events in the natural world, and to use those explanations to make useful predictions.

Scientific thinking usually begins with observation

Observation - use of the senses to gather information

Data – evidence; the information gathered from observations.

Data can be broken down into two categories:

  • Quantitativedata are expressed as numbers, obtained by counting or measuring.

    • Ex.100mL water

  • Qualitative data are descriptiveand involve characteristics that can't usually be counted.

    • Ex.A blue sky

What is an Inference?

When you do something with an observation:

Draw a conclusion

Offer an explanation

The scientific method was developed because people started asking questions about everyday events and wanted answers….VALID answers.

How Scientists Work

What is the Scientific Method?

  • The basic plan or procedure a scientist follows when conducting an experiment

Parts of an experiment

“Students who study every day learn more in school.”

What are the parts of an experiment to test this statement?

Parts of an experiment

“Students who study every day learn more in school.”

  • Independent variable (IV): the variable YOU control:

    • Whether or not students study

Parts of an experiment

“Students who study every day learn more in school.”

Dependent Variable (DV): the variable that changes because of the IV

Student learning in school

Parts of an experiment

“Students who study every day learn more in school.”

Constant: the things that do not change among the test subjects

Same teacher, same subject…what are some more?

Parts of an experiment

“Students who study every day learn more in school.”

  • Control: the group you do NOT experiment on

    • Is there a clear control here?

Step Number One:

  • Ask a question or find a problem

    • How can students perform better in school?

Step 2:

  • Observation/Research

    • How do you check student performance?

    • What are the best students doing?

Step 3: Formulate a hypothesis

  • Using the ‘if…then…’ formula:

  • If students study, then they will do well in school.

Step 4:

  • Experiment: develop and follow a procedure

  • Test your hypothesis

  • The outcome must be measurable (quantifiable)

Step 4 continued:

  • Collect DATA

    • You will probably need a DATA TABLE

Step 4 continued:

Use many trials:

Study many students

Step 5:

  • Analyze your results:

    • Make a graph or a chart

Step 6

  • Draw a Conclusion: include a statement that accepts or rejects the hypothesis

Step 7

  • Communicate results

    • Write a paper in a scientific journal

  • You guys will write a LAB REPORT

It looks like this:

Parts of an experiment ON A GRAPH

What goes here?


Doing better in school



Types of Graphs

  • Line graph: used (usually) to show a change over time

Types of Graphs

  • Bar graphs are used (usually) to compare different subjects

Types of Graphs

  • Pie graphs are used to compare parts of a whole

Causes of Death Among Humans:

What are the parts of the student studying experiment?

  • Whether or not they studied every day is the

    • independent variable

  • The students’ performance is the

    • dependent variable

  • Keeping the subject/time spent studying/school the same is the

    • Constant

If a hypothesis is not testable…

  • It is NOT science!

A sample Experiment:

An ecologist with the Environmental Protection Agency (EPA) wants to investigate whether acid rain has an affect on the hatching rate of salamander eggs. The scientist incubates 1000 salamander eggs in mildly acidic pond water (pH = 6) and another 1000 salamander eggs in regular, neutral pond water (pH = 7). The water temperature, amount of dissolved oxygen, and light was kept the same among all groups. All eggs were given 63 days to develop.

  • Independent Variable:

    • the pH of the water

  • Dependent Variable:

    • the hatching of salamander eggs

  • Constants:

    • water temperature, dissolved oxygen, light, and time

  • Control Group:

    • 1000 eggs in neutral pond water

  • Trials:

    • 1000 eggs in mildly acidic water

One more thing:

  • It’s best to use several trials with each independent variable

  • Why?

  • Design an experiment consisting of a control and three different experimental groups to test the prediction, “Tulips grow better as the amount of fertilizer in which they are grown increases.” In your answer, be sure to:

  • Name the control:

  • Describe the three experimental groups:

  • State one way to determine if the hypothesis is correct:

  • Describe one example of experimental results that would support the hypothesis.

  • What is the independent variable and the dependent variable in this problem?

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