The Scientific Method

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Introduc on

Lab 1
The Scien

c Method
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Lab 1 : Scien

c Method

Concepts to explore:

Concepts to explore:

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Testable observa ons
Hypothesis
Null hypothesis
Experimental approach
Variables
Controls

Data collec on
Analysis

Introduc on
What is science? You have likely taken several classes throughout your career as a student, and know that it is more than just chapters in a book. Science is a process that uses evidence to understand the history of the natural world and how it works. It is constantly changing as we understand more about the natural world, and con nues to advance the understanding of the universe. Science begins with ob serva ons that can be measured in some way so that data can be collected in a useful manner by follow ing the scien c method.

Have you ever wondered why the sky is blue or why a plant grows toward a window? If so, you have al ready taken the rst step down the road of discovery. No ma er what the ques on, the scien c meth od can help nd an answer (or more than one answer!). Following the scien c method helps to insure scien sts can minimize bias when tes ng a theory. It will help you to collect and organize informa on in a useful way, looking for connec ons and pa erns in the data. As an experimenter, you should use the scien c method as you conduct the experiments throughout this manual.

Figure 1: The process of the scien

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c method

Lab 1 : Scien

c Method

The scien c method process begins with the formula on of a
hypothesis – a statement of what the experimenter thinks will happen in certain situa ons. A hypothesis is an educated guess – a proposed explana on for an event based on observa on(s). A null hypothesis is a testable statement, that if proven true means the hypothesis was incorrect. Both statements must be testable, but only one can be true. Hypotheses are typically wri en in an if/ then format, such as:

Hypothesis:
If nutrients are added to soil, then plants grown in it will Figure 2: What a ects plant growth?
grow faster than plants without added nutrients in the soil. Null hypothesis:
If nutrients are added to the soil, then the
plants will grow the same as plants in soil
without added nutrients.

If plants grow quicker when nutrients are added,
then the hypothesis is accepted and the null
hypothesis is rejected.

There are o en many ways to test a hypothesis.
When designing an experiment to test a hypothesis
there are three rules to follow:
1. The experiment must be replicable.
2. Only test one variable at a me.
3. Always include a control.

Variables are de ned and measurable components of an experiment. Controlling the variables in an experiment allows the scien st to quan tate the changes that occur so that results can be measured and conclusions drawn. There are three types of variables:

Independent Variable: The variable that the scien st changes to a predetermined value in order to test the hypothesis. There can only be one independent variable in each experiment in order to pinpoint the change that a ects the outcome of the experi ment.

Dependent Variable: This variable is measured in regards to condi ons of the inde pendent variable—it depends on the independent variable. There can be more than one dependent variable in each experiment.

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Lab 1 : Scien

c Method
Controlled Variable: This variable, or variables (there could be many) re ect the factors that could in uence the results of the experiment, but are not the planned changes the scien st is expec ng (by changing the independent variable). These variables must be controlled so that the results can be associated with some change in the independent variable.

When designing the experiment, establish a clear and concise procedure. Controls must be iden ed to eliminate compounding changes that can in uence the results. O en mes, the hardest part of design ing an experiment is not guring out how to...
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