Types of Scientific investigations and the nature of science

1. Scientific
Investigations
& the Nature of
Science

3. Types of Science Investigations
 Descriptive investigation: involves describing and/or
quantifying parts of a natural or man-made system
 Comparative investigation: involves collecting data
under different conditions (e.g., times of year,
temperatures, locations) to make a comparison
 Experimental investigation: involves designing a fair
test in which variables are actively manipulated,
controlled, and measured in an effort to gather
evidence to support or not support a causal
relationship

4. Using a Science Investigation
 Observation
 Hypothesis
 Experiment
 Sample size
 Controls
 Constants
 Variables – independent and dependent (DRY
MIX)
 Data Collection and Analysis
 Type of graphs, SI System (metric system)
 Retesting
 Placebo, blind studies, peer review
 Theories and Laws
 When hypotheses are confirmed through
repeated scientific experiments
 Can be changed when more data becomes
available

5. What do we believe?
 Who is reporting the information?
 Who conducted the research?
 Who paid for it?
 Is the report based on reputable
research and repeated experimentation?
 CDC
 National Institute of Health
 WHO
 Is the report based on testimonials or
personal experiences?
 Are the claims too good to be true?

6. Evaluating an Experiment
A research group is studying the effect of energy drinks on
the pulse rate of adolescents. Twenty five students were
selected, ages 14-18. Each had their resting pulse rate
measured and then consumed an energy drink such as Red
Bull. After 1 hour, their pulse rate was tested again and
compared to the original rate.
Control:
Constants:
Independent Variables
Dependent Variables:
How could this experiment be improved?
Would you trust the outcome of this experiment?

7. Evaluating an Experiment,
sample 2
Miracle Gro ™ is developing a new form of fertilizer that is
specific to helping tomato plants grow. They obtained 100
tomato plants to test their new fertilizer on. Each plant was
watered daily with 10mL of water and placed in a
greenhouse where it received the same amount of sun.
Group A plants received 10mL of the fertilizer, Group B
plants received 5mL of the fertilizer, and Group C plants
received no fertilizer. Plant growth was measured for one
month.
Control:
Constants:
Independent Variables
Dependent Variables:
How could this experiment be improved?
Would you trust the outcome of this experiment?

8. Review
 What are observations based on?
 What are hypothesis based on?
 Why should scientists always re-test?
 What is the point of a peer review?
 How do scientists come to conclusions?
 Why do good experiments need a control
or placebo?
 How can uncontrolled variables lead to
faulty data?
 Why does the U.S. spend billions of
dollars each year on scientific research?
Should they?

9. Nature of Science
Empirical - Scientific
knowledge is, at least
partially, based on
and/or derived from
observations of the
natural world
Archaeopteryx
Pangaea

10. Nature of Science
Observations and Inferences:
Observations are descriptive
statements about natural
phenomena that are “directly”
accessible to the senses (or
extensions of the senses).
By contrast, inferences are
statements about phenomena
that are not “directly”
accessible to the senses.
Charles Darwin
And “his” finches

11. Nature of Science
Tentativeness – Scientific knowledge changes in
two ways; it grows as new knowledge is
discovered and improves as old knowledge is
revised corrected.
While scientific knowledge is
tentative, there is also much
reliability in scientific knowledge
because of its empirical basis.

12. Nature of Science
Social/Cultural Embeddedness -
Science is practiced in the context
of a larger culture and scientists are
the product of that culture.
Science is affected by the
various elements of the culture
in which it is embedded.
These elements include social
fabric, power structures, politics,
socioeconomic factors, philosophy,
and religion.
Stem Cell Research & HPV Vaccine

13. Nature of Science
Subjectivity - Scientific knowledge is
subjective.
Scientists’ theoretical commitments,
beliefs, previous knowledge, training,
experiences, and expectations
actually influence their work.
Scientists’ observations (and
investigations) are always motivated
and guided by, and acquire meaning in
reference to questions or problems.
H. pylori
Drs. Barry Marshall
& Robin Warren

14. Nature of Science
Creativity - Scientific
knowledge involves human
imagination and creativity.
Science involves the
invention of explanations
and this requires a great
deal of creativity by
scientists.
Dr. Bonnie Bassler-
Bacteria Communication

15. Nature of Science
Theories and Laws - Theories and
laws are different kinds of knowledge;
one can not develop or be transformed
into the other.
Laws are statements or descriptions of
the relationships among observable
phenomena (the “what”).
Theories, by contrast, are inferred
explanations for observable
phenomena (the “how”).

16. Look at these two sets
of animal tracks.
List 3 OBSERVATIONS
Make an INFERENCE

17. Now what do you think?
Make 3 OBSERVATIONS
Make an INFERENCE

18. Now what do you think?
Make 3 OBSERVATIONS
Make an INFERENCE