Science and scientific method 400

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

Science

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

Uses the scientific method

Conclusions rely on data and facts

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

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

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

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

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!

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

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

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

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

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