Science as a Process

Designing ExperimentsSee also SaP Google Presentation

What goes into Good Science?

Experimental Design• Start with a question.

• Do background research.

• Develop your hypothesis.

• Determine what the variables are and how you will measure them quantitatively (with numbers).

• Identify your control (if applicable).

• Write your procedure.

• Prepare data tables.

• Collect data (perform experimentation).

• Graph data.

• Analyze and discuss data. Was your hypothesis true?

Variables• Variable – values in an experiment

that can change• Control – group in an experiment

where all variables are kept the same with no changes; typically this is the “normal” condition–Controls are used so that you can

compare normal and experimental groups

• Independent variable – the variable that scientists purposefully change; the variable that is being “tested” or “questioned”

• Dependent variable – the responding variable; the variable that changes as a result of the independent variable

– The changes in the dependent variable are caused by the independent variable.

Example

• Question: Which color of light makes plants grow the highest in length: red, green, or white?

• What is the independent variable? • What is the dependent variable?

• Use the following sentence to figure out the variables.

• The ____________ changes the _____________.Independent

variableDependent

variable

Qualities of Good experiments…

They…..

•have multiple trials (typically requires finding averages).

•have quantitative data (numerical).

•test only one independent variable and one dependent variable.

•should be able to be repeated by other scientists.

Rules For Graphs

• Independent variable goes in the X-axis. (remember Index)

• Dependent variable goes in the Y-axis.• Label both axes and include units.• Give the graph a descriptive title.• Use a key or legend if needed.• Scale must include all data points.• The scale on an axis must have equal intervals.

Rules For Tables

• Label the columns and rows. • Include units.• Give the table a descriptive title.

Scientific Terms

• Hypothesis - a proposed, scientifically testable explanation for an observed event.– Example: Red light will make plants grow 50%

taller than green light and 25% taller than white light.

• Inference - a conclusion based on observations, knowledge, and scientifically tested hypotheses– Example: After collecting data it was found that

white light caused plants to grow taller than red or green lights.

• Law or principle- an explanation of scientific events that can be explained using mathematics and is observed to be the same throughout the universe– Example: First Law of Thermodynamics -

energy cannot be created nor destroyed…– Example: Principle of segregation – describes

how genes separate in forming sperm and eggs

• Theory - a widely tested and accepted explanation of science ideas based on observation, measurement, and logic– Example: Cell theory – all life is made up of

cells…