The Scientific Method

SOL Standards for Scientific Investigation in Biology The 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;

BIO SOLs: sources of error inherent in experimental design are identified and discussed; 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. A way to gather empirical evidence.

The Basic Steps of the Scientific Method

1. Make an observation… Notice something in your environment (immediate, local, regional, or global) that makes you wonder… EX: My breath is not always good in the morning

2. State the problem… Form a question about a specific event or reaction EX: Could that be because of bacteria? Mouthwash kills bacteria. Which brand works best?

3. Collect Information Research the problem or… Conduct an experiment or… Make additional observations EX: Read the labels of 3 common brands of mouthwash and see which has the most antiseptic (germ-killing) ingredients.

4. Form a hypothesis Make an educated prediction based on your research. A hypothesis can be recognized by an “if, then” statement. EX: If Listerine has more antiseptic ingredients than Scope or Wal-Mart brand, then it will kill more bacteria.

5. Design an Experiment Devise a way to test your hypothesis. Create a CONTROLLED experiment.

ONLY 1 condition is changed! 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!

Note that not all experiments require a control group… …when comparing multiple independent variables against each other there is no control.

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 Experiment Control Group -no mouthwash Experimental Group Petri dish Bacteria grown from swab Listerine Experimental Group Scope Wal-Mart brand

Mouthwash Experiment INDEPENDENT VARIABLE: Type of Mouthwash Amount of bacteria killed

6. 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

QUANITATIVE EX: Area of Inhibition for Mouthwash Brands 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 mm 10 min 4 mm 15 min 6 mm 5 mm 20 min 8 mm

7. Draw Conclusions Determine from the data collected if the hypothesis was supported or un-supported 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 multiple experiments over time show a hypothesis to be supported, other scientists may accept it as 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 - 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 EX: Newton’s Law of Gravity

Progression of Ideas in Science Which one is most likely to be wrong- hypothesis, theory, or law? 1. 2. 3. Hypothesis Theory Law

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