the scientific method. goal what is the scientific method? what does the scientific method assume?...

The Scientific Method

Goal

• What is the scientific method?• What does the scientific method

assume?• Does the scientific method work?• What is not a scientific argument.

The Scientific Method

1. Observe an event.2. Develop a model (or hypothesis) which

makes a prediction.3. Test the prediction.4. Observe the result.5. Revise the hypothesis.6. Repeat as needed.7. A successful hypothesis becomes a

Scientific Theory.

model

test

Steps to Solving a Problem

(The Scientific Method)1. Identify the Problem• State the problem to be solved or the question to be answered.

2. Collect Information/Research• Obtain facts and ideas from books, journals, internet, etc. that

provide insight regarding your problem/question. Cite these resources.

3. Form a Hypothesis• Based on the information/research you collect, propose a solution or

“best guess” that will help guide your experimentation and attempt to answer the proposed problem/question.

4. Test Your Hypothesis – “Experiment”• Describe, design, and conduct an experiment that will give you

information or data that supports (or not) your hypothesis.5. Accept or Reject Your Hypothesis – “Analysis”

• Determine whether your data/results from the experiment supports (or not) your hypothesis; if not, it may be necessary to review your information/research and revise your hypothesis.

6. Report Your Results – “Conclusion”• Formulate a conclusion that answers the original question from step

one and share the results with the scientific community (or the community at large).

Observations

• data that are descriptions of qualities such as shape, color, taste, feel, etc…

• acquired by using your senses• Two Types:

1. Objective observation 2. Subjective observation

2 Types of Observations

Objective

• an observation based on fact

fact – a piece of information that can be strictly defined and proved true.

Subjective

• an observation based on opinion

opinion – a statement that expresses a belief, value, or feeling

Objective or Subjective?

• Which type of observations should be used in science?

Objective observations should be used in science because they are based on facts and the basis of science is to identify the facts!

Objective or Subjective?• Science looks like fun today!

Subjective• Kanye West’s songs sound good!

Subjective• The counter-tops in class are black!

Objective• School French fries taste good!

Subjective• The summer was too short!

Subjective• There are sixty seconds in a minute!

Objective

Inference• an explanation that tries to make sense of

your observations • influenced by your experiences/prior

knowledge• these explanations may not be true

ExampleObservation:

John was breathing heavily as he walked into the classroom.

Possible Inferences: 1. He ran to class because he was going to be late

2. He just played basketball in gym

What would you infer?

1. Everyone is closing their book because…

2. Many students buy French fries because…

3. Students arrived to class sweaty because…

4. All of the students are laughing because…

Hypothesis• a working explanation or trial answer to a

problem • an “educated guess”• can be written in the form of an “If..., then...,

because...” statement• is not necessarily proven correct just because

data/results from one experiment supports it

Example

If an individual increases his/her activity level, then their heart rate will increase because the body’s muscles (cells)

will require more oxygen to function at a higher level. A faster beating heart will increase blood flow; thus, allowing an increased concentration of oxygen to reach the cells in

need.

Data

• factual information• Two Types

1. Quantitative2. Qualitative

2 Types of Data

Quantitative• data consisting of

numbers

Example

Heart rate (80 beats/minute)

Qualitative• data consisting of

verbal descriptions or information gathered using scales without numbers

Examples

Verbal description of heart rate (fast or slow)

Repeated Trials

• experimental tests done more than once• necessary to provide more accurate results;

data is averaged together• lessens the impact of a chance error on the

experimental results

Examples

In the heart rates lab each participant recorded their heart rates after performing various activities. Each

participant’s data (for resting, walking, and running) represents a trial. If five total individuals performed the activities and gathered data, then there were a

total of five trials.

Two Types of VariablesIndependent

• variables that are purposely changed or manipulated in an experiment

• the factor that you wish to test

• usually expressed after the word “if” in the hypothesis

• could be thought of as the “cause” in a cause and effect relationship

Example

The activity level (resting, walking, running)

Dependent

• variables that may change as a result of the independent variable

• the factor you measure to gather results

• usually expressed after the word “then” in the hypothesis

• could be thought of as the “effect” in a cause and effect relationship

Example

The person’s heart rate

Identify the Variables

1. If a student chooses to not study, then they will earn a poor grade.

2. If you drink Gatorade before a soccer game, then you will score more goals.

3. If you increase the mechanical advantage of a pulley system used to move an object, then the input force becomes less.

independent variable

dependent variable


dependent variable


dependent variable

Control or Control Group• a group of subjects in an experiment that are not

given any special treatment• something that is not manipulated• same as the experimental group in every possible

way, except for the factor being tested • a neutral point of reference for comparison – it

allows you to see what changing a variable does by comparing it to not changing anything.

Example

The resting heart rate represented the baseline heart rate to which any increase in activity level was compared to.

Constants

• Factors in an experiment (both in the experimental and control groups) that are kept the same and not allowed to change

Examples

1. One minute was consistently the amount of time allotted to perform the necessary activity2. The type of activity performed

3. The stopwatch used during data collection4. The method used to measure the heart rate

Medical ScienceScientific Method

High Cholesterol

Observation Patient has high cholesterol

Hypothesis (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.

Everyday Science

Scientific Method Car Repair

Observation Engine won’t turn over.


Predict battery is dead.

Test Replace battery.

Observe result Engine now turns over.

Revise hypothesis? Not needed.

New test? Not needed.

Scientific Theory Cars won’t work without a fully charged battery.

Everyday Science

Scientific Method Making Spaghetti Sauce

Observation Spaghetti sauce should be red.


Try a tomato sauce.

Test Heat pot of tomato sauce.

Observe result Taste the sauce - bland.

Revise hypothesis? Use tomato sauce and garlic!

New test? Add garlic, taste - not so bland.

Scientific Theory The Final Recipe.

Food Science

• Throwing something together Hypothesis

• Your grandmother’s time-tested recipe Scientific Theory.

Repeatability

• A successful theory is repeatable.– By you.– By anyone.

Requirements

• Objective reality– We all see the same world.

• Constant Laws of Nature– What happens here, happens there.– What happened yesterday will happen

tomorrow.• The Cosmos is knowable.

Does it work?

• Scientific Method is a tool.• Does this tool work?

– Life expectancy– Mortality rates

• Are there better tools?

Theories

• So: a theory is a highly successful hypothesis.

• All hypotheses make predictions.• All theories make predictions.• All theories can be tested.• Result: Any scientific theory is subject

to change as our ability to make tests, or make observations of a test’s results, improves with time.

Non-scientific Theories

• Make no predictions• Un-testable• Can’t be falsified


• Car won’t work? Aliens drained the battery.

• Spaghetti is bland? You were meant to eat bland food.

• Car won’t work? Gods must be angry.• Spaghetti is bland? At the instant of

tasting, tongue is transported to alternate dimension where all flavors are rendered nullified. Happens instantaneously.


• The chain of events needed for life to arise is too complicated to have happened by chance, a divine intelligence must therefore have caused life to arise (Intelligent Design).

• Face on Mars.

Viking Orbiter (1976) Mars Global Surveyor (1998)

Falsification

• A real Scientific Theory tells you what observations are necessary to falsify it.– Not so proponents of:

• Face on Mars• Moon Hoax• Intelligent Design• Astrologers