The Scientific MethodVirginia Standard of Learning BIO.1a-m

BIO SOL: 1 a-mThe student will plan and conduct investigations in which:

• observations of living organisms are recorded in the lab and in the field;

• hypotheses are formulated based on direct observations and information from scientific literature;

• variables are defined and investigations are designed to test hypotheses;

• graphing and arithmetic calculations are used as tools in data analysis;

• conclusions are formed based on recorded quantitative and qualitative data;

• sources of error inherent in experimental design are identified and discussed;

BIO SOL: 1 a-mThe student will plan and conduct investigations in which:

• validity of data is determined;• chemicals and equipment are used in a safe manner;• appropriate technology including computers, graphing

calculators, and probeware, is used for gathering and analyzing data and communicating results;

• research utilizes scientific literature;• differentiation is made between a scientific hypothesis

and theory;• alternative scientific explanations and models are

recognized and analyzed; and• a scientific viewpoint is constructed and defended (the

nature of science).

The Scientific Method• An organized way to solve a

problem through experimentation & observation.

The 6 Steps of the Scientific Method

1. State the Problem• Form a question about a specific

event or reaction

EX: Mouthwash kills bacteria. Which brand works best?

2. Collect Information• Research the problem

EX: Read the labels of 3 common brands of mouthwash and see which has the most antiseptic (germ-killing) ingredients.

3. Form a hypothesis• Make an educated guess based on

your research.

EX: If Listerine has more antiseptic ingredients than Scope or Wal-Mart brand, then it will kill more bacteria.

A hypothesis can be recognized by an “if, then” statement.

4. Design an Experiment• Devise a way to test your hypothesis.

Create a CONTROLLED experiment.

• A controlled experiment MUST have 2 groups.

CONTROL GROUP: all conditions remain the same

EXPERIMENTAL GROUP: only the condition that you are testing for is changed

ONLY 1 condition is changed!

• Establish the variables for your experiment.

INDEPENDENT VARIABLE: the variable that is changed, manipulated (X axis for graphing)

DEPENDENT VARIABLE: the change caused by the manipulation of the independent variable (Y axis for graphing)

Mouthwash ExperimentPetri dish

Bacteria grown from swab

Control Group -no mouthwash

Experimental Group

Listerine

Scope

Wal-Mart brand

Mouthwash Experiment

INDEPENDENT VARIABLE:

DEPENDENT VARIABLE:

Type of Mouthwash

Amount of bacteria killed

5. Collect & Analyze Data• Run the experiment & document the

data

• 2 Types of Data

QUANTITATIVE: numerical data, deals with specific quantities, usually in the form of a graph or chart

QUALITATIVE: descriptive data, describes how something looks, smells, sounds, or feels; deals with qualities

QUALITATIVE EX: The control group and the Wal-Mart brand have a strong smell; the Listerine & Scope don’t smell as bad.

QUANITATIVE EX: Area of Inhibition for Mouthwash Brands Control Listerine Scope Wal-Mart

5 min 0 mm 3 mm 2 mm 1 mm10 min 0 mm 4 mm 3 mm 3 mm15 min 0 mm 6 mm 5 mm 4 mm20 min 0 mm 8 mm 6 mm 4 mm

6. Draw Conclusions• Determine from the data collected if

the hypothesis was correct or incorrect

EX: Listerine did kill more bacteria than the other brands because it had more antiseptic ingredients.

Progression of Ideas in Science• Hypothesis- a possible explanation

to a question based on information the scientist has already gathered

- If experiments show a hypothesis to be correct, other scientists may accept it as support for a scientific theory.

EX: Plants obtain their energy from the sun.

Progression of Ideas in Science

• Scientific Theory- a general statement of why things work based on hypotheses that have been tested many times

Progression of Ideas in Science

- Theories are used to explain & predict the outcome of other experiments

- Theories must be tested

- Sometimes they are wrong & must be modified or discarded

EX: The Earth is flat.

Progression of Ideas in Science

• Scientific Law- a statement of what happens in a certain event based on verified observations & experiments

Progression of Ideas in Science- Explains what happens & not why

EX: Newton’s Law of Gravity

- Summaries of the results of many, many experiments & observations

- When results of a series of experiments are the same each time they no longer need to be tested

Progression of Ideas in Science• Which one is most likely to be

wrong- hypothesis, theory, or law?

Hypothesis Theory Law

1. 2. 3.

Scientific Method Vocabulary• Observation- the act of observing

(touch, taste, smell, feel, see, etc.)• Inference- a quick conclusion that

attempts to explain an observation• Prediction- to forecast; to guess the

outcome of a situation beforehand

• Analysis- to separate or break apart into smaller sections for study

Scientific Method Vocabulary• Conclusion- to close or bring to an

end; to accept or reject a hypothesis in an experiment

• Data- recorded observations or measurements

• Hypothesis- a tentative explanation that accounts for a set of facts & that can be tested by further investigation

Scientific Method Vocabulary• Theory- an explanation of a large

body of information, experimental and inferential, and serves as an overarching framework for numerous concepts. It is subject to change as new evidence becomes available.

• Law- a basic scientific theory that is no longer tested & is generally accepted as true (Newton’s Law of Gravity)

Scientific Method Vocabulary• Controlled Experiment- an

experiment in which all variables except the ONE being tested are identical in order to make the experiment fair & the results reliable

• Variable- any factor in an experiment that could affect the results & is therefore tested separately

Scientific Method Vocabulary• Controlled Variable- a variable that

is not changed

• Independent Variable – a variable that you purposely manipulate (manipulated variable)

• Dependent Variable- the variable being observed that changes in response to the independent variable (responding variable)

Scientific Method Vocabulary• Quantitative Data- data that

involves numbers or measurement usually in the form of a chart or graph

• Qualitative Data- anecdotal or descriptive data that does NOT involve numbers or measurement