Scientific Method

http://www.teachersdomain.org/asset/drey07_int_scprocess/

Big Ideas in……Scientific Thinking• Science is a collection of facts and a process for understanding

the world. • A beginner’s guide: what are the steps of the scientific method? • Well-designed experiments are essential to testing hypotheses. • Scientific thinking can help us make wise decisions. • What are the major themes in biology?

Categories of Science

• Pure Science– Study of naturally

occurring things solely for the purpose of knowing and discovery

– Biology– Chemistry– Physics– Astronomy– Geology

• Applied Science– Science which gathers

information for practical uses

– Medical science– Engineering– Forensic Science

Types of Science

• Inductive Reasoning– Discovery science– Make a broad

generalization– Then provide

observations to support generalization

– Conclusion reached from specific examples

• Deductive Reasoning– Hypothesis-Driven– Conclusion reached from

general statements– Design experiment to test

hypothesis– “All organisms are made of

cells”– “Humans are organisms”– Therefore……– “Humans are made of cells”

http://www.socialresearchmethods.net/kb/dedind.php

Are You a Scientist?• Does the radiation released by cell phones cause brain damage?• Do large doses of vitamin C reduce the likelihood of getting a cold?• Why is morning breath so stinky? And can you do anything to

prevent it?• Why is it easier to remember gossip than physics or math

equations?• Which parent determines a baby’s gender? Why?• What is “blood doping” and does it really improve athletic

performance?• Why is it so much easier for an infant to learn a complex language

than it is for a college student to learn biology?

What is Science?

• “An intellectual activity, encompassing observation, description, experimentation, and explanation of natural phenomena.”

• A way to come to discover and better understand our world

Real World Science

• Cause of autism (Time)• Climate change (The Economist)• Steroids & kids (Newsweek)• DNA Profiling

Superstition

• What is superstition?• Why do people believe in superstitions?• What are some common superstitions you

believe in?• Should superstitions supported by science?

Scientific Method• Ask a question from observations

– Process of examining and discovery– Observation of phenomena

• Formulate hypothesis– Propose explanation or answer to a question

• Devise a testable prediction• Design an experiment• Draw conclusion & make revisions

– Replicate

• Apply to real world

Observations• Observations of nature or our surroundings

spark questions

Redi’s Experiment• Observation: Flies land on meat that is left

uncovered. Later maggots appear on the meat.

Research/Background • Scientist gather background information to

gain ideas & explanations about the problem• Use books & scientific journals to find data

related to observation which may lead to solution of problem

• What information would Redi need to research?

Forming a Hypothesis

• A hypothesis is a proposed explanation or answer to a set of observations

• Must be testable (design experiment)• Redi’s hypothesis:“Flies produce maggots”

Controlled Experiment

• Control Group– All conditions remain unchanged (placebo)

– The data is used to compare to experimental group

– What were the controlled variables in Redi’s experiment?

Experimental GroupContain the ONE factor that is changed in the experiment (cause)

• It tests the independent variable (manipulated variable)

• The variable that was deliberately changed/altered

• Where is the manipulated located on a graph?

• x-axis

• The dependent variable (responding variable)

• Variable that is measured in response to independent variable

• Where is the responding variable located on a graph?

• y-axis

• What was the independent variable in Redi’s experiment?

• Covered jar• What was the dependent variable in Redi’s

experiment?• Presence of maggots

Data Collection

• DATA recorded on charts, tables and graphs.

• Qualitative (description using senses)• Quantitative (number based)

Data

• What qualitative data would Redi collect?• What quantitative data would Redi collect?

Results/Data• A scientist carefully collects and organizes data from the experiment.

• Data should always be presented in a neat fashion, usually tables or graphs.

• NO OPINION!

• In the graph on the right, what is the dependent variable ? What is the independent variable?

Conclusion

• Scientific work is only valid if it can be verified again and again

• Summarize your finding using evidence from experiment.– Was your hypothesis supported/refuted?– What are possible errors in experiment?– What conclusions can you make based on data table/graphs?– Revision of hypothesis– How could these findings be applicable to real world issues?– http://www.ket.org/education/video/watersolutions/scientifi

cmethod.htm

Medical ScienceScientific Method

High Cholesterol

Observation Patient has high cholesterolHypothesis (prediction)

Certain chemicals may dissolve cholesterol deposits.

Test Give 100 patients these chemicals, give 100 patients placebo.

Observe result Same number lower their cholesterol as placebo patients.

Revise hypothesis?

Try different combo of chemicals.

New test? Re-run medical test. Observe results.

Scientific Theory

Lipitor reduces cholesterol.

• A logical explanation for events that occur in nature that have been supported by NUMEROUS experiments.

• Published and accepted in scientific community• Note: This is not the same definition for theory in

other subjects.• Replication is essential to validity and acceptance