2. •Experimental Design Research – The
manipulation and control of variables
• You absolutely, positively have to know
what the variables are!
1. What you are changing?
• How you are changing it?
2. What you are measuring?
• How you are measuring?
3. Repeated trials
4. Data tables

3. So an experimental question has
to indicate the variables:
1. How the independent variable
will AFFECT the dependent
variable
2. What the EFFECT of the
independent variable
will be on the
dependent variable

4. For example…
•How does the temperature of
ocean water affect the speed of a
hurricane?
Independent variable is the
temperature of ocean water.
Dependent variable is the
speed of a hurricane.

5. • Descriptive Design Research - Based
mainly on observations.
Ex.
1. Making models
2. Dissections
3. Observing animals in the wild
Specific Example: How do the survivors
of a disaster react to the disaster?
No variables; data is based on
watching and talking to survivors

7. •Good questions come from
careful observations.
•Questions beginning with
what, why, how and when are
very important in focusing
on an investigation.

8. •An observation is any
use of the senses to
gather information.
•Observations may be
direct or indirect.

9. •Direct observations are
made using one of your
senses such as sight or touch.
•Indirect observations are made by
using an instrument such as a
thermometer or a microscope.

10. •Observations usually lead to
inferences.
•An inference is a logical
interpretation based on
observations or prior
knowledge (schema).

11. •Example of an
observation: Shadows
can change in length.
•Example of an inference: The
length of an object’s shadow
depends on how near the object
is to the light source.

12. •Determine if the
following examples are
observations or
inferences.
•You do not have to write these in
your notes.

13. I turn on a fan.
The blades of the fan
are turning.

14. There is a whirring sound.

15. You feel a breeze.

16. The fan is pushing the
air around in the room.

18. •A hypothesis is a clear statement of
what you EXPECT the answer to your
question to be.
•Your hypothesis will represent your
best “educated guess” based on what
you have observed and what you
already know (schema).
•A hypothesis must be stated in an if-
then format.

19. A hypothesis is a special kind of
prediction.
o What makes it so special???
• It’s a guess about the VARIABLES&
their relationship, in particular,
•How will the independent
variable affect the dependent
variable?

20. Here is an example of a
hypothesis:
If the researcher uses acid
rain to water plants, then
the plants’ growth will be
slower.

21. Do NOT use
personal pronouns!!
Ithink that acid rain
causes plants to grow
more slowly.

22. •Hypothesis
− a statement that uses a few observations
− an idea based on observations without experimental
evidence
•Theory
− uses many observations and has lots of experimental
evidence
− can be applied to unrelated facts and new relationships
− flexible enough to be modified if new data/evidence is
introduced
•Law
− stands the test of time, often without change
− experimentally confirmed over and over
− can create true predictions for different situations
− has uniformity and is universal

24. • You test your hypothesis
by doing an experiment.
• Make sure you are doing
an experiment and not a
demonstration!

25. •Though modeling a
volcano’s eruption
is an interesting
demonstration, it is
NOT an experiment.
•Experiment vs. Demonstration
•Figuring out how altitude
affects the boiling point of water
is an experiment.

26. A controlled experiment tests
only ONE factor.
• A controlled experiment has a
control group and one or more
experimental group.
• The control group and the
experimental groups are
EXACTLY the same except for
ONE factor.

27. • The factor that differs is
called the variable.
• Because the variable is the
only factor that differs,
scientists know that this factor
is responsible for the results of
the experiment.

28. •An independent variableis what
the scientist changes in the
experiment.
•A dependent variableis what
changes in the experiment as a
result of what the scientist does.

29. •While doing the experiment, be
sure to write down all of the
observations that you make.
•Include any type of measurement
using the metric system.
•EX: time, date, height, size,
amount, temperature, etc.

30. •Be as exact as possible in
taking measurements.
•Measure something more
than once and use the
average of the results.

31. Test More than One Subject!
• Sample size is the number of
subjects you test.
•Your sample size must be large
enough to allow you to draw
accurate conclusions from your
data.

32. •Do Multiple Trials!
•When doing an
experiment, perform each
test several times.

34. After you have
collected your data,
determine what it
means.

35. Tables and graphs are often useful
in helping to organize the data.
Distance Rolled for a Metal Sphere

36. All graphs should include:
•Title
•Label the axis
•Include a key (legend)
•Use distinct colors

37. •Every graph always needs a
key so people can easily
tell what each color or
pattern represents.

38. 0
10
20
30
40
50
60
70
80
90
Week 1 Week 2 Week 3
Full Light
Light deprived
Tomato Plant Height

39. In a line graph, place the
dependent variable on the
vertical axis and the
independent variable on the
horizontal axis.

40. 0
10
20
30
40
50
60
1 2 3 4
Sample 1 Sample 2 Sample 3
Temperature Variation over 4 Hours

41. •Showing percentages is
easy to do with a pie chart.
•You can quickly see which
group has the biggest slice
and therefore contains the
most data.

42. People
who
sneezed
43%
People
who
didn't
sneeze
57%
Sneezing After Exposure to
10 Minutes of Bright Light

44. •Based on the analysis of your
data, you should conclude
whether your results reject
or support your hypothesis.
•If the data does reject or
support the hypothesis, why
do you think it does?

45. •REMEMBER that it is NOT
important for the hypothesis to be
correct.
•What is important is that you
explain WHY you got the results you
did.
•Be sure to mention in your
conclusion what factors you believe
contributed to your results.

46. •Briefly explain possibilities for
new experiments that would
control these factors.
•Also, mention any investigative
questions that came up during
the experiment.

48. •Report your results by
doing a written report.
•Let others know what
you have learned.
•Once again, DO NOT
use personal pronouns!!

49. • Be sure to include a
bibliography, and no, Wikipedia is
NEVER an acceptable source for
any project throughout the entire
year!
• Give credit to the people who
helped you in your project- your
teacher, your parents,
professional scientist, or others.