The Scientific MethodThe Scientific Method

An overviewAn overview

What is Science?

“Science” derived from Latin ‘to know’Way of asking and answering questionsSeeking answers to questions about

natural phenomena (we are therefore limited to what kinds of questions we ask)

Scientific thinking reduces emotional reactions

Forms of Scientific Inquiry

Discovery or Descriptive Science– Observation– Qualitative vs. Quantitative data

Types of Logic

Inductive Reasoning– Derive generalizations based on specific

observations

Types of Logic

Inductive Reasoning– Derive generalizations based on specific

observationsDeductive Reasoning

- Specific predictions follow from general premise

Forms of Scientific Inquiry

Discovery or Descriptive Science– Observation– Qualitative vs. Quantitative data

Hypothesis-Based Science

Scientific Design

Scientific knowledge begins with an observation and a proposed explanation.

Explanation called a hypothesisA hypothesis is testable and falsifiable In science hypotheses are tested by using

them to make predictions about how a particular system will behave

Theories and Natural Laws

Theory: a description of the world that covers a relatively large number of phenomena and has met many observational and experimental tests

Law of Nature: theory (or group of theories) that has been tested extensively and seems to apply everywhere in the universe-they become part of the conceptual framework of a particular field

Scientific Method in Action

We use the scientific method in everyday life

Example:

You got in your car to drive up here and turned the key but the car wouldn’t start (observation)

Scientific Method in Action

Example:

You got in your car to drive up here and turned the key but the car wouldn’t start (observation)

Hypothesis: There is something wrong with the car

Scientific Method in Action

Example:

You got in your car to drive up here and turned the key but the car wouldn’t start (observation)

Hypothesis: There is something wrong with the car

Predictions: battery dead, ignition problem,

out of gas

Scientific Method in Action

Test predictions: turn on headlights, check spark plug wires, dip stick in gas tank

Scientific Method in Action

Test predictions: turn on headlights, check spark plug wires, dip stick in gas tank

Analyze results: headlights work, strong ignition spark, no gas on dip stick-gas gauge reads half full

Scientific Method in Action

Test predictions: turn on headlights, check spark plug wires, dip stick in gas tank

Analyze results: headlights work, strong ignition spark, no gas on dip stick-gas gauge reads half full

Draw conclusion: gauge inaccurate, out of gas

Important terms:

Independent (manipulated) variable: condition or event under study (choose 1) .Graphing-x axis

Dependent (responding) variable: condition that could change under the influence of the independent variable (measure this). Y-axis

Controlled variables: conditions which could effect the outcome of the experiment so they must be held constant between groups.

experimental group: group(s) subjected to the independent variable

control group: group not subjected to the independent variable, used as measuring stick

reproducibility: producing the same result consistently to verify result. It is therefore important to describe your experimental design in enough detail for others to perform the same experiment.

Example

Hyp: King’s collar repels fleasPred: dogs wearing King’s collar will have

fewer fleas than those without collar

IV: King’s collar DV: presence of fleas

CV’s: anything that might effect the number of fleas on the dogs

Can we think of some???

Experimental Design• Obtain 500 dogs of various breeds from

local shelters. Have vet weed out the 200 dogs with the most fleas. Randomly assign individuals to 2 groups.

• Board the dogs in identical environments and treat them the same except that one group gets to wear the King collar and the other group does not

• After 2 wks. The dogs are examined by a vet for fleas.

Results: the dogs wearing the King collars were virtually free of fleas after the 2 wk period compared to the dogs without the collars which had about the same number of fleas as when the experiment began

• Assumptions: factors thought to be true for the investigation but have not been verified or controlled– Commonly accepted information– Thought to be held constant but not controlled– Factors beyond the investigators control because of

technical or time considerations– Sometimes called confounding variables

• Incorrect assumptions invalidate an experiment!