The Scientific MethodLecture 2 8-13-14

I CAN explain the steps of the scientific method and identify variables involved in experimental study.

Introduction to the Scientific Process

The Scientific Method is a logical, systematic approach to solving a scientific problem.

Overview of the Scientific Process

Conclusions can lead to revising the existing hypothesis or developing a new hypothesis.

Step 1: Identify a Problem Observe the world around you.

• Using observations, identify a problem you would like to solve.• This is a question you DO NOT know the answer to

and can’t look up and must be testable. “Why” and “What would happen if…” are good

beginnings of scientific questions.

Step 2: Gather Information

Use references to do background research. (Do not need to reinvent the wheel!)

Books Journals Magazines Internet TV Videos Interview Experts

Step 3A: Formulate a Hypothesis

Possible answer to a question that can be tested.

Based on observations and knowledge.“If” “Then” or “Because” statement.

Step 3B: Formulate a Null Hypothesis

It’s very possible that a hypothesis will NOT be supported by the research.

An experiment also has a NULL HYPOSTHESIS – this is a statement that says there is NO RELATIONSHIP BETWEEN THE VARIABLES being studied in the experiment.

Step 4: Develop an Experiment

An EXPERIMENT is a procedure designed to TEST A HYPOTHESIS.

•Organized, well thought out, step by step process.

Can take place in a LABORATORY or in the FIELD.

Involves a number of VARIABLES – factors that can change the outcome of the experiment.

The MANIPULATED VARIABLE is the factor that the experimenter CHANGES to observe its effect(s).

Sometimes called the Independent Variable.

Variables: Manipulated Variable

Variables: Responding Variable

Changes in response to the manipulated variable.

Is measured in the experiment.Sometime called the Dependent

Variable.

Variables: ConstantAll the factors in the experiments

that are kept the same are known as CONSTANTS.

Everything except the manipulated and responding variables.

Keeps the experiment “fair”.

The normal condition that you compare the responding variable to.

Allows the experimenter to decide the effects of the manipulated variable.

Variable: Control Group

Step 5: Record and Organize Data

Write down all observations and measurements.

NEVER destroy data!Use tables/graphs/charts to organize your

data.Label Everything including manipulated

and responding variables.

Step 6: Analyze Data

EXAMINE the data collected. Does it SUPPORT the hypothesis?

YES

1.Repeat experiment.

2.Have others conduct same experiment.

NO

1.Repeat experiment.

2.Review/discard hypothesis.

A student in Mrs. Wright’s agriculture class wants to know if Miracle Grow fertilizer will help tomato plants grow larger than a generic brand from Wal-Mart. The student plants three plots of 20 plants each. One receives Miracle Grow, one the generic brand and the third no fertilizer. The height of the plants is measured and recorded every three days for 6 weeks.

1. What would be a valid hypothesis for this experiment?2. What would be a null hypothesis for this experiment?3. Why did the third group of plants get no fertilizer at

all?4. What are some controls in this experiment?

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