2. Nature of Science
“Science is a particular way of knowing about the world. In science, explanations are limited to those based on observations and experiments that can be substantiated by other scientists. Explanation that cannot be based on empirical evidence are not part of science.”
The National Academy of Sciences

3. Nature of Science Science is based on experimentation
The development of an experiment tends to follow the Scientific Method
Ask a question
Conduct background research
Construct a hypothesis
Test your hypothesis in an experiment
Analyze Data
Draw conclusions and communicate them

4. Ask a question – often based on observations
Observation: Description of something you can see, smell, touch, taste, hear
NOT an opinion!! (must be objective)
Example:
The ground is wet
Inference: A guess about an object or outcome based on your observations
You can make many inferences from a single observation
Example:
It rained.
Someone was watering the plants

5. Practice: Make observations and inferences about the picture.

6. Ask a question – observations are either…
Qualitative Observation: describes qualities
Examples:
Green liquid
Large hole
Sour taste
Sweet smell
Quantitative Observation: uses numbers to measure something
Examples:
4 feet long
6 legs
7.2 grams
100 mL

7. Practice: Make qualitative observations, quantitative observations, and inferences about the picture.

8. Considerations for Quantitative Data
Quantitative data must be…
PRECISE = how close your measurements are to each other (think consistent or specific)
ACCURATE = how close your measurement is to the correct/accepted value (think correct)
Always give the most specific reading on your instrument, then estimate one more decimal place

9. Precise but not Accurate
Precise and Accurate
Precise but not Accurate
Practice: Label the different bulls-eyes.
Accurate but not Precise
Not Accurate or Precise

10. Conduct background research – define a Purpose/Objective
The GOAL of scientific investigations is to answer a question
Observations  Questions  Research (what has already been found?)  Purpose
Purpose/Objective is a statement that clearly shows what question you are trying to answer in your investigation

11. Construct a Hypothesis
Hypothesis: A testable prediction based on observations (more than a guess!!) that describes a cause and effect relationship between variables
Format for a Hypothesis:
“IF (IV) then (DV) “
IV = Independent variable = Cause
DV = Dependent variable = Effect

12. Defining Independent and Dependent Variables
Independent Variable: (IV) what the experimenter will deliberately change or manipulate in the investigation
The X-Axis on a graph
It is the ONLY thing different between different experimental groups
Ex. You want to do an experiment to see if what you drink before a race affects how quickly you run.
What is the IV?

13. Defining Independent and Dependent Variables
Dependent Variable: (DV) what changes in response to the independent variable
The Y-Axis on a graph
Usually represented by the data you collect in an investigation; what is measured
Ex. Recall the running experiment.
What is the DV?

14. Test your hypothesis in an experiment- Materials
What will you need to conduct the experiment?
Include amounts
Include brands, if important
Be as specific as possible!
Write as a bulleted list

15. Test your hypothesis in an experiment- Procedures
Write out every step that was taken
Start with an action word
Include every step so that someone could replicate the experiment
Make this a numbered list
When designing experimental procedures you must ALWAYS consider…
Experimental Group: groups that are being tested
What is the experimental group in the running example?

16. When designing experimental procedures you must ALWAYS consider…
Control Group: group used for comparison with your experimental groups. This is the “normal” group
What is the control group in the running example?
Constants: the aspects of an experiment that are held constant/consistent
Ensures that all aspects of trials are identical, except for the IV
Ensures that any difference measured in the DV is caused only by the IV
Ex. All runners should be the same age, gender, same breakfast, same training, same shoes, etc.

17. When designing experimental procedures you must ALWAYS consider…
Repeated Trials to:
Ensure the results aren’t due to chance
Eliminate any errors
Ensure the data is precise

18. Analyze Data – Results and Analysis Results
Collect data in an organized form during an investigation (ex. Data Table)
Present data in a graph
Analysis
Only make statements about what the data shows
Do NOT state in analysis whether your hypothesis was “right” or “wrong”
Include any errors you made

19. Draw conclusions and communicate them
Make an explicit statement about whether your hypothesis was supported or rejected by your experimental data
Data may support your prediction
Data may fail to support (reject) your prediction
NOTE: Data does NOT prove/disprove
State the real world application.