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Scientific Method and Experimental Design
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Page 1: Scientific Method and Experimental Design

Scientific Method and Experimental Design

Page 2: Scientific Method and Experimental Design

Goal of Science

Steps of Scientific Method

Hypothesis

Independent and Dependent Variable

Experimental Design

Sample Size and Validity

Data Collection and Organization

Conclusions

The Characteristics of Science

Page 3: Scientific Method and Experimental Design

ScienceA process, based on observations and experimentation, that provides explanations of natural events or problems

Uses the scientific method

Conclusions rely on data and facts, inferences and observations

Page 4: Scientific Method and Experimental Design

Steps of the Scientific Method

1. Make observation

2. Question/problem

3. Background research

4. Hypothesis

5. Experiment/observe

6. Collect and analyze data

7. Conclusion

8. Retest

9. Publish

Page 5: Scientific Method and Experimental Design

An possible explanation of a natural event or observation that can be tested by additional observations or experimentation

Must be testable!

Written as “If……., then……” statement

Hypothesis

Page 6: Scientific Method and Experimental Design

Identify 2 crucial variables to write hypothesis

Independent variable: The factor that is deliberately manipulated in an experiment (also called experimental variable)

• “Presumed cause”

Dependent variable: The variable that changes in response to changes in the independent variable. It is what is measured in the experiment

• “Presumed effect or result”

Hypothesis

Page 7: Scientific Method and Experimental Design

Hypothesis

Hypothesis is written as follows:

If independent variable, then dependent variable

Ex. If 100 grams of fertilizer is applied to a lawn, then the lawn will grow at a faster rate.

IV amount of fertilizer

DV rate of growth

Page 8: Scientific Method and Experimental Design

Controlled Experiments

Tests one variable at a time (experimental variable)

Controlled experiments include 2 groups:

Experimental Group

Exposed to experimental variable

Control Group

Not exposed to experimental variable, all variables held constant

All extraneous variables must be held constant in both groups!

Page 9: Scientific Method and Experimental Design

Sample Size (N)

•The number of subjects involved in experimentation

•Increasing N

• Decreases impact of chance events and error

• Increase reliability of results (validity)

Sample Size

Page 10: Scientific Method and Experimental Design

The extent to which experimental results can be generalized to other settings or situations

To increase validity, increase N

Ex. 7 tanks, 6 experimental and 1 control

Each tank has 100 single celled green organisms

All variables held constant except the light

Validity

Page 11: Scientific Method and Experimental Design

Quantitative Data: numerical data

Ex. Measurement of depth in inches

Qualitative Data: descriptive data

collect with your senses

Ex. Color

Use data tables and charts to more effectively display data for analysis

Record and Analyze Data

Page 12: Scientific Method and Experimental Design

Conclusion

Refers back to the hypothesis

“Supported” or “rejected”

Use data to support

If the same conclusions are supported over a long enough period of time they become theories

Page 13: Scientific Method and Experimental Design

Scientific Theories

Explanation for a natural event

Based on observation, experimentation, inference, and evidence

Explains current observations and predicts future events

Page 14: Scientific Method and Experimental Design

The Characteristics of Science

1. Based on the assumption that the natural world can be investigated and explained in terms we can understand.

2. Based on the results of controlled experimentation and observations.

3. The results must be repeatable and verifiable.

4. Must be refutable. If a hypothesis is not supported by evidence it must be rejected or re-worded

Page 15: Scientific Method and Experimental Design